IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: Saladin on May 04, 2010, 12:44:39 pm

Title: S1 and S2 DOUBTS HERE!!!!
Post by: Saladin on May 04, 2010, 12:44:39 pm
Hey, I do Edexcel S1, please post all your doubts here!!!
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on May 08, 2010, 06:47:30 pm
Here's this question! I was solving through the book exercises and then I found this question a bit confusing.

A farmer keeps a record of the weekly milk yield of his herd of seven cows over a period of 6 months. He finds that the mean yield is 24 liters. He buys another cow that he is told will produce 28 liters of milk in a week. Work out the effect this will have on the mean milk yield of his cows.

Thank you in advance.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Summer :] on May 09, 2010, 05:15:31 pm
i just face difficulties in answering those questions requiring comments :(
dunno what to do about it!! and those type of questions are more common nowdays then in the old papers  >:(
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 09, 2010, 06:31:30 pm
Here's this question! I was solving through the book exercises and then I found this question a bit confusing.

A farmer keeps a record of the weekly milk yield of his herd of seven cows over a period of 6 months. He finds that the mean yield is 24 liters. He buys another cow that he is told will produce 28 liters of milk in a week. Work out the effect this will have on the mean milk yield of his cows.

Thank you in advance.


It will increase his yield to 24.5
\frac{24*7+28}{8}
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 09, 2010, 06:32:46 pm
i just face difficulties in answering those questions requiring comments :(
dunno what to do about it!! and those type of questions are more common nowdays then in the old papers  >:(

It is best just to understand what the question is essentially asking. What is the question trying to investigate...

Sometimes, it just comes with practice.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Summer :] on May 10, 2010, 07:21:36 am
It is best just to understand what the question is essentially asking. What is the question trying to investigate...

Sometimes, it just comes with practice.
yeah true that..i prefer the C2 its more challenging  :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 17, 2010, 12:18:02 pm
help plz

Given that \mu=27  and \sigma^2= 10


find P(26 < X < 28).


my answer was  0.251

but in the MS the answer is 0.0796
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 17, 2010, 05:27:46 pm
Here is how you get it:

\frac{26-27}{\sqrt{10}}=-0.3162

\frac{28-27}{\sqrt{10}}=0.3162

Therefore,

The Probability is P(-0.3162<X<0.3162)

Therefore, P(X<0.32)= 0.6255

1-0.6255

0.3745*2

0.749

If I was using actual values, instead of statistical tables, I would have gotten your answer.


Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 17, 2010, 06:00:38 pm
help plz

Given that \mu=27  and \sigma^2= 10


find P(26 < X < 28).


my answer was  0.251

but in the MS the answer is 0.0796


Which paper did you get this from?
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 17, 2010, 06:01:18 pm
help plz

Given that \mu=27  and \sigma^2= 10


find P(26 < X < 28).


my answer was  0.251

but in the MS the answer is 0.0796

As per da MS dey hve taken S.D frm  \sigma^2= 10  as 10
but 10 is da variance, so da MS is wrong.While ur ans is correct.
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 17, 2010, 06:10:42 pm
Which paper did you get this from?

jan 2004 q2
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 17, 2010, 06:12:00 pm
As per da MS dey hve taken S.D frm  \sigma^2= 10  as 10
but 10 is da variance, so da MS is wrong.While ur ans is correct.


ya , i also think the MS is wrong
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 17, 2010, 06:12:17 pm
jan 2004 q2

Will check again, I dont think I am wrong though.

How did you get ur answer?
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 17, 2010, 06:17:04 pm
Will check again, I dont think I am wrong though.

How did you get ur answer?

same as ur method

but at the end u have to subtract

1-0.749=0.251
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 17, 2010, 06:21:20 pm
Will check again, I dont think I am wrong though.

How did you get ur answer?

paper link S1 jan 04 (http://www.srepapmaxeeeerf.org/A%20Level/Maths/Edexcel/S1/S1%202004-01.pdf)
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 17, 2010, 06:27:00 pm
Da MS smetimes tends 2 b wrong.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 17, 2010, 06:29:54 pm
same as ur method

but at the end u have to subtract

1-0.749=0.251

oops, forgot that part. heheheh.
Title: Re: S1 DOUBTS HERE!!!!
Post by: solo_G on May 21, 2010, 04:04:18 am
okay guys i have a doubt....
of the customers visiting the stereo section of a large electronic store 75% on average make a purchase....find the least possible number of customers, given that the probability of all customers making a purchase is less than 5%
thanks in advance  ;D
Title: Re: S1 DOUBTS HERE!!!!
Post by: solo_G on May 21, 2010, 04:21:41 am
ehm ehm one more doubt ;D ;D
A license plate has 3 letters and 3 digits in that order.A witness to a hit and run accident saw the first 2 letters and the last digit.If the letters and digits can be repeated,how many license plate should be checked before finding the culprit?
ANS: 2600

Thanks again ;D
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 21, 2010, 08:05:23 am
ehm ehm one more doubt ;D ;D
A license plate has 3 letters and 3 digits in that order.A witness to a hit and run accident saw the first 2 letters and the last digit.If the letters and digits can be repeated,how many license plate should be checked before finding the culprit?
ANS: 2600

Thanks again ;D

###***
26C1=26(choosing da last remaining letter)
10C1*10C1=100(choosing both digits,dey cn b repeated)
26*100=2600
Title: Re: S1 DOUBTS HERE!!!!
Post by: solo_G on May 21, 2010, 03:46:35 pm
###***
26C1=26(choosing da last remaining letter)
10C1*10C1=100(choosing both digits,dey cn b repeated)
26*100=2600
aye aye i see...thanks immortal!
+1 rep! ;D
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 21, 2010, 03:58:14 pm
U're welcome :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 21, 2010, 05:06:58 pm
okay guys i have a doubt....
of the customers visiting the stereo section of a large electronic store 75% on average make a purchase....find the least possible number of customers, given that the probability of all customers making a purchase is less than 5%
thanks in advance  ;D

P(x=n)<0.05
= (0.75)^n<0.05

take log on both sides
log(0.75)^n<log(0.05)
nlog(0.75)<log(0.05)
n(-0.28768)<-2.99573
when we convert negative to positive the inequality reverses
n>2.99573/0.28768
n>10.4134
n>11
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 21, 2010, 05:08:18 pm
I have doubt ladies and gentlemen

November 2003 paper 6
Question 4 part 3
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 21, 2010, 05:23:34 pm
19/20*19/20*1/20

Da first & second card cn b any expect da 1 he wants
da third one he gets da one he wants...afterward it does not matter.. 
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 21, 2010, 09:15:43 pm
19/20*19/20*1/20

Da first & second card cn b any expect da 1 he wants
da third one he gets da one he wants...afterward it does not matter.. 

I thought of the same after i got my first answer wrong

I was confused because he bought a total of 5 cards right

so couldnt it be 3C1(19/20)^2(1/20) as he stopped looking at cards after the third one?
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 21, 2010, 09:48:37 pm
I thought of the same after i got my first answer wrong

I was confused because he bought a total of 5 cards right

so couldnt it be 3C1(19/20)^2(1/20) as he stopped looking at cards after the third one?
I advice u 2 think simple :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 21, 2010, 10:34:18 pm
I advice u 2 think simple :)

lol
right :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on May 22, 2010, 09:18:24 am
What's the formula booklet that the edexcel board will give us during the examination?? or did they stop doing that??
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 22, 2010, 09:22:45 am
What's the formula booklet that the edexcel board will give us during the examination?? or did they stop doing that??

i will post it soon

and yes you will be given it
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on May 22, 2010, 09:23:34 am
i will post it soon

and yes you will be given it
Okay then :) thank you :D
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 22, 2010, 01:36:30 pm
need help in this question


jan 08

Q3
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 22, 2010, 02:25:01 pm
need help in this question


jan 08

Q3

I'm on it now.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 22, 2010, 02:47:37 pm
need help in this question


jan 08

Q3

First you have to calculate the area under the bars.

(1*6)+(1*7)+(4*2)+(2*6)+(3*5.5)+(5*2)+(3*1.5)+(12*0.5)

=70

Therefore, now calculating the number of people per unit area.
\frac{140}{70}=2

Work out the area in the interval given.

0.5*12*

6*2

12
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 22, 2010, 04:09:52 pm
First you have to calculate the area under the bars.

(1*6)+(1*7)+(4*2)+(2*6)+(3*5.5)+(5*2)+(3*1.5)+(12*0.5)

=70

Therefore, now calculating the number of people per unit area.
\frac{140}{70}=2

Work out the area in the interval given.

0.5*12*

6*2

12

thanx:)
Title: Re: S1 DOUBTS HERE!!!!
Post by: solo_G on May 23, 2010, 06:59:41 am
P(x=n)<0.05
= (0.75)^n<0.05

take log on both sides
log(0.75)^n<log(0.05)
nlog(0.75)<log(0.05)
n(-0.28768)<-2.99573
when we convert negative to positive the inequality reverses
n>2.99573/0.28768
n>10.4134
n>11
thanx freaked!! hehehe nice nickname!! ;D +1 rep  ;D :D
Title: Re: S1 DOUBTS HERE!!!!
Post by: solo_G on May 23, 2010, 07:02:05 am
aight people anotha Qs  ;D
its from nov 09 varient 1
find how many numbers between 5000 and 6000 can be formed from the digits 1,2,3,4,5,6 if  repition of digits is allowed......i dnt get why is it 6 to da powr of 3? ??? ??? ??? >:(
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 23, 2010, 07:32:23 am
must start with 5 then there are three other digits from a choice of 5 so 5*4*3
this is in the ms. You are looking at the wrong answer
Title: Re: S1 DOUBTS HERE!!!!
Post by: solo_G on May 23, 2010, 07:48:30 am
must start with 5 then there are three other digits from a choice of 5 so 5*4*3
this is in the ms. You are looking at the wrong answer
oh sorry sir i meant for the second question.........if reptitions ARE allowed....thanks
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 23, 2010, 09:48:54 am
aight people anotha Qs  ;D
its from nov 09 varient 1
find how many numbers between 5000 and 6000 can be formed from the digits 1,2,3,4,5,6 if  repition of digits is allowed......i dnt get why is it 6 to da powr of 3? ??? ??? ??? >:(
Its a 4 digit num between 5000-6000
So da last 3 digits r changed wit those of da range..
Dat is each zero haz 6C1 different variables.
4 all 3 zero's 6C4*6C1*6C1=63
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 24, 2010, 03:41:22 am
Its a 4 digit num between 5000-6000
So da last 3 digits r changed wit those of da range..
Dat is each zero haz 6C1 different variables.
4 all 3 zero's 6C4*6C1*6C1=63


So immortal how did you find S1 past papers so far?
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 24, 2010, 03:16:49 pm
So immortal how did you find S1 past papers so far?
y do u ask ???
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 24, 2010, 10:06:15 pm
y do u ask ???
I dont know
Title: Re: S1 DOUBTS HERE!!!!
Post by: simba on May 25, 2010, 09:54:53 am
need help in June 09 number 1 , how to get Z....urgent
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 25, 2010, 11:33:26 am
When i get home
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 25, 2010, 11:40:43 am
need help in June 09 number 1 , how to get Z....urgent
Which paper is this frm??
Title: Re: S1 DOUBTS HERE!!!!
Post by: simba on May 25, 2010, 06:32:55 pm
nvm abt last one....I would like to know how to solve question 5 in Nov.09 first varient......urgently
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 25, 2010, 07:08:02 pm
I think this question waz already answered b4/
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 25, 2010, 07:19:57 pm
5a)
i>  no digits repeated range 5000-6000
      so 5xxx r da possibilities, 1,2,3,4,5,6    5 cannot b used
     remaining ones 5P3 as arrangement matters 4 numbers.

ii> repeated digits   all num frm 1-6 cn b used
         5xxx     so  5(6c1)(6c1)(6c1)
        so 6*6*6 num cn b formed dat is 63
Title: Re: S1 DOUBTS HERE!!!!
Post by: simba on May 25, 2010, 07:25:54 pm
mmmmm...another question in  Nov.09 first varient num.3..
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 25, 2010, 07:27:01 pm
5b)
i>  mor girls dan boys
   so   3g   2b
         4g   2b
         5g   0b

8c3*6c2+8c4*6c2+8c5
=1316

ii>Total of 8+6=14 students  11 if cousins r ignored.
   with cousins  11C2(wit 3 cousins already included)
   without dem   11C5
  so  55+462
       =517
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 25, 2010, 07:28:01 pm
mmmmm...another question in  Nov.09 first varient num.3..
Will ans in 15min
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 25, 2010, 07:31:55 pm
P(85 < x < 100)
                                         
           = 0.5 – P  [z < {(85 ? 100)/7}]           
                                                                   
                       
           = 0.5 – P (z < – 2.143)                     
           = 0.5 – (1 – ?(2.143))
           = 0.9839 – 0.5
           = 0.484       
Title: Re: S1 DOUBTS HERE!!!!
Post by: simba on May 25, 2010, 07:45:10 pm
why is it times 0.5..
Title: Re: S1 DOUBTS HERE!!!!
Post by: simba on May 25, 2010, 08:04:07 pm
another question in Nov.09 2nd varient num.1.....how to get standard  deviation ???
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 25, 2010, 08:11:40 pm
why is it times 0.5..

because its
100-100
---------
     7
which is zero

.The value of p corresponding to zero is 0.5
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 25, 2010, 08:15:14 pm
part two of Question 3 is also very easy
its states that 33 percent of times are the longest and smallest
so value of p of the middle is 0.34.

1-0.34=0.67
which is +-0.67
(a-100)/7=0.67

will give u the maximum time
(a-100)/7=-0.67
will give you the least time
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 25, 2010, 11:24:05 pm
i doubt anyone is awake
but if there is anyone on
answer the second variant of november 2009
question 4
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 25, 2010, 11:38:01 pm
Can you post the paper? My file is corrupted.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 25, 2010, 11:54:34 pm
Can you post the paper? My file is corrupted.

Find how many different odd numbers greater then 500 can be made using some or all of the digits 1,3,5 and 6 with no digit being repeated

I did it but it took me half an hour to figure it out

But your output could proove to be valuable :D
Title: Re: S1 DOUBTS HERE!!!!
Post by: khi2ruh on May 26, 2010, 01:29:14 am
hey im stuck!!

n09 Q5 (a) (i) (ii) and b (ii)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 26, 2010, 08:11:46 am
hey im stuck!!

n09 Q5 (a) (i) (ii) and b (ii)

Sorry m8, I do Edexcel.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Sweet_03 on May 26, 2010, 09:17:33 am
Hello , can someone plz help

June2005
Q7 (d)

P( sci | RH ) = P(sci 'n' RH) / P(RH) = (24÷110)/ (110÷148)
thats wat i did , but obviously its wrong
how do you find P(sci 'n' RH) ???
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 26, 2010, 10:07:12 am
Hello , can someone plz help

June2005
Q7 (d)

P( sci | RH ) = P(sci 'n' RH) / P(RH) = (24÷110)/ (110÷148)
thats wat i did , but obviously its wrong
how do you find P(sci 'n' RH) ???

On it now, will be finished soon iA.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 26, 2010, 10:39:15 am
Hello , can someone plz help

June2005
Q7 (d)

P( sci | RH ) = P(sci 'n' RH) / P(RH) = (24÷110)/ (110÷148)
thats wat i did , but obviously its wrong
how do you find P(sci 'n' RH) ???

This is how you do it.

(c)You have to find the number of people that are right handed.

\frac{80}{100}*30+\frac{75}{100}*68+\frac{70}{100}*50=110

So, there are a total of 110 right handers, and a total of 148 students.

So, \frac{110}{148}=0.743

(d) This is basically asking, out of 110 right handers, what is the probability that it will be a science student?

So, the number of science students that are right handed, are \frac{80}{100}*30=24

Now, \frac{24}{110}=0.218
Title: Re: S1 DOUBTS HERE!!!!
Post by: Sweet_03 on May 26, 2010, 02:08:47 pm
Oh! i was trying to use the formula
okay now it makes sense =')
thank you
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 26, 2010, 02:23:01 pm
Oh! i was trying to use the formula
okay now it makes sense =')
thank you

Sometimes, you need to understand the whole concept, and understand the feel of the question before attempting it.
Title: Re: S1 DOUBTS HERE!!!!
Post by: immortal on May 26, 2010, 02:33:40 pm
Sometimes, you need to understand the whole concept, and understand the feel of the question before attempting it.
this also saves a lot of time..
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 26, 2010, 02:42:07 pm
this also saves a lot of time..

Just doin ma job.  8)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Summer :] on May 26, 2010, 02:54:36 pm
Find
E( x^2 + 4X - 3)
E(x) = 2.6
and the answer = 15.6
how did they get it ?????
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 26, 2010, 02:59:23 pm
Find
E( x^2 + 4X - 3)
E(x) = 2.6
and the answer = 15.6
how did they get it ??
You must know the variance to answer this question. What is it?
Title: Re: S1 DOUBTS HERE!!!!
Post by: coatseville on May 26, 2010, 03:06:55 pm
I have two questions...
From the January 2009 paper
question 3e) could you please explain fully how to do this..
and for 2b) why must we use the addition rule? When we didnt in 2a)
Thankyou SO much :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Summer :] on May 26, 2010, 03:20:52 pm
Find
E( x^2 + 4X - 3)
E(x) = 2.6
and the answer = 15.6
how did they get it ??
You must know the variance to answer this question. What is it?

Var 1.44
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 26, 2010, 03:37:37 pm
Find
E( x^2 + 4X - 3)
E(x) = 2.6
and the answer = 15.6
how did they get it ??
You must know the variance to answer this question. What is it?

Var 1.44
V(X0=E(X^2)-(E(X))^2
1.44=E(X^2)-2.6^2
E(X^2)=1.44+6.76=8.18
E( x^2 + 4X - 3)=E(X^2)-4E(X)-3=8.18-4*2.6-3=8.18-1.4=-5.22
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on May 26, 2010, 03:53:28 pm
June 2001
Question 1 a)
they said to find the mean and the standard deviation for the data given
in the markscheme they gave something different to what i solved
the mean i knew how to do but the standard deviation was the weird part

My solution : Standard Deviation = Square root of [(sum of x^2 divided by n)-(mean)^2]
my answer gives me Math Error

and in the markscheme the answer comes out 4 :/
plz someone help asap
thank you
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 26, 2010, 04:07:51 pm
I dont have the cie 2001 jun paper. Can you upload it here?
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on May 26, 2010, 04:16:51 pm
I dont have the cie 2001 jun paper. Can you upload it here?
not the cie the edexcel
6683 code
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 26, 2010, 04:40:45 pm
sd=sqrt(sum x^2/n -mean^2)
=sqrt(46625/25-(1075/25)^2)=4
mistak in question sum x^2 should be 46625.
Dont blame me. I only stole them
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 26, 2010, 04:41:34 pm
not the cie the edexcel
6683 code

Each of the 25 students on a computer course recorded the number of minutes x, to the nearest minute, spent surfing the internet during a given day. The results are summarised below.

            \sum x=1075,\sum x^2=46625

(a) Find \mu and \sigma for these data.                         
(3)  
Two other students surfed the internet on the same day for 35 and 51 minutes respectively.

(b) Without further calculation, explain the effect on the mean of including these two students.             


for part a  

\mu=\frac{1075}{25}

\mu=43

\sigma^2=\frac{46625}{25}-(43^2)
\sigma=4
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on May 26, 2010, 04:45:50 pm
Each of the 25 students on a computer course recorded the number of minutes x, to the nearest minute, spent surfing the internet during a given day. The results are summarised below.

            \sum x=1075,\sum x^2=46625

(a) Find \mu and \sigma for these data.                         
(3)  
Two other students surfed the internet on the same day for 35 and 51 minutes respectively.

(b) Without further calculation, explain the effect on the mean of including these two students.             


for part a  

\mu=\frac{1075}{25}

\mu=43

\sigma^2=\frac{46625}{25}-(43^2)
\sigma=4

nvm nvm!! lol
thank you T.Q!!
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 26, 2010, 05:10:10 pm
FROM NOW ON, ALL QUESTION PAPERS WILL BE ASSUMED TO BE EDEXCEL, UNLESS TOLD OTHERWISE.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on May 26, 2010, 07:36:37 pm
edexcel june 2009 question 3
i dont understand how they got the width
Title: Re: S1 DOUBTS HERE!!!!
Post by: insane.kid on May 26, 2010, 08:14:13 pm
Hello ppl i have som doubts plz can u try to solve them they are :
1) year 2002 june 6th question
2) year 2005 june 4th question
3) year 2007 june 2e) with explanation and reason

Plz reply soon ppl and best of luck for ur exam :D
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 26, 2010, 08:22:44 pm
Hello ppl i have som doubts plz can u try to solve them they are :
1) year 2002 june 6th question
2) year 2005 june 4th question
3) year 2007 june 2e) with explanation and reason

Plz reply soon ppl and best of luck for ur exam :D

answering now.
Title: Re: S1 DOUBTS HERE!!!!
Post by: insane.kid on May 26, 2010, 08:32:55 pm
Thanks you Engraved for ur help cld u even help in normal distribution or if u have any good notes cld u plz attach it thanks a ton though :D may God bless u and ur exam goes well :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saladin on May 26, 2010, 08:59:57 pm
Hello ppl i have som doubts plz can u try to solve them they are :
1) year 2002 june 6th question
2) year 2005 june 4th question
3) year 2007 june 2e) with explanation and reason

Plz reply soon ppl and best of luck for ur exam :D

June 2007

The mean is the average of the 3 quartiles=45

\frac{X-\mu}{\sigma}=Z

\frac{54-45}{\sigma}=0.67

Check the log table for the step above.

13.43
Title: Re: S1 DOUBTS HERE!!!!
Post by: insane.kid on May 26, 2010, 09:09:11 pm
Engraved y did u pick 54 or how did u knw u had to takee tht ?
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on May 26, 2010, 09:42:32 pm
how do we calculate the width and the height of a rectangle representing a group class modal ???
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on May 26, 2010, 09:44:11 pm
I just did CIE S1 today
so if you could just write down the whole question i will FOR SURE solve it
Title: Re: S1 DOUBTS HERE!!!!
Post by: T.Q on May 26, 2010, 09:54:03 pm
edexcel june 2009 question 3
i dont understand how they got the width

u have to find out the scale factor
 or solve it proportionally   
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 26, 2010, 10:32:23 pm
for histograms use
height_2/height_1=frequency density_2/frequency density_1

length of base_2/length of base_1=length of interval_2/length of interval_1
Title: Re: S1 DOUBTS HERE!!!!
Post by: insane.kid on May 26, 2010, 10:34:38 pm
astarmathsandphysics cld u plz solve these two question edexcel stats
1) year 2002 june 6th question
2) year 2005 june 4th question
thank u
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 26, 2010, 10:35:28 pm
one mo.
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 26, 2010, 10:58:25 pm
those two questions above
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on May 26, 2010, 11:46:01 pm
see also

http://www.astarmathsandphysics.com/igcse_maths_notes/igcse_maths_notes_calculating_the_dimensions_of_histogram_bars.html
Title: Re: S1 DOUBTS HERE!!!!
Post by: insane.kid on May 27, 2010, 09:57:29 am
Sorry for the late reply thanks a lot astar :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Blizz_rb93 on August 28, 2010, 01:10:58 pm
i dont get interpolation, can someone explain to me the exact steps of what to do
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on September 08, 2010, 09:28:37 am
I will do a page on interpolation for stats.
Here is a page also http://www.astarmathsandphysics.com/a_level_maths_notes/FP1/a_level_maths_notes_fp1_linear_interpolation.html

I will do the stats page tomorrow
Title: Re: S1 DOUBTS HERE!!!!
Post by: ::~A!i~:: on October 15, 2010, 04:52:37 pm
A discrete random variable is such that each of its values is assumed to be equally likely.

(a)Write down the name of the distribution that could be used to model this random variable.
(b)Give an example of such a distribution.
(c)Comment on the assumption that each value is equally likely.
(d)Suggest how you might refine the model in part (a).

Can someone please explain, im confused..?
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 15, 2010, 11:28:40 pm
a)discrete uniform
b)SCORE ON A DICE
c)perfectly possible
d)throw the dice 1000000000000000000000 times and find from this
the probability of scoring each of 1,2,3,4,56,
Title: Re: S1 DOUBTS HERE!!!!
Post by: Baladya on October 23, 2010, 08:42:09 am
Hey long time no c all :)

So looks like AS isn't that easy after all. Year is gonna be full of doubts :D

Anyway,

http://www.xtremepapers.net/CIE/International%20A%20And%20AS%20Level/9709%20-%20Mathematics/9709_s09_qp_6.pdf (http://www.xtremepapers.net/CIE/International%20A%20And%20AS%20Level/9709%20-%20Mathematics/9709_s09_qp_6.pdf)
Q6)ii) I drew the graph and decided to put the sign which means that there is skipped values on the y axis... Is this okay? like doesnt this change the shape of the first part of the graph?

Thanks
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 23, 2010, 10:17:28 pm
hu
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 07, 2010, 09:31:51 am

7. A committee of 6 people, which must contain at least 4 men and at least 1 women, is to be chosen from 10 men and 9 women.

i) Find the number of possible committee that can be chosen. [3]

ii) Find the probability that one particular man, Albert and one particular woman, Tracey are both on the committee.[2]

iii) Find the number of possible committees that include either Albert or Tracey but not both. [3]

iv) The committee that is chosen of 4 men and 2 women. They queue up randomly in a line for refreshments. Find the probability that the women are not next to each other in the queue. [3]
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on November 09, 2010, 02:53:48 pm
I am giving Exams for S1 this May/June. (2011)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on November 09, 2010, 11:24:58 pm
Can you help with this question, please?

7. A committee of 6 people, which must contain at least 4 men and at least 1 women, is to be chosen from 10 men and 9 women.

i) Find the number of possible committee that can be chosen. [3]
(6P1+8P1)*6!
ii) Find the probability that one particular man, Albert and one particular woman, Tracey are both on the committee.[2]

iii) Find the number of possible committees that include either Albert or Tracey but not both. [3]

iv) The committee that is chosen of 4 men and 2 women. They queue up randomly in a line for refreshments. Find the probability that the women are not next to each other in the queue. [3]

Let me work out the rest
Title: Re: S1 DOUBTS HERE!!!!
Post by: Freaked12 on November 09, 2010, 11:33:08 pm
Oh

This is already done
sorry
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ivo on November 10, 2010, 08:02:59 pm
A dice is known to be biased in such a way that, when it is thrown, the probability of a 6 showing is \frac{1}{4}.  This biased dice and an ordinary fair dice are thrown.  Find the probability that exactly one of the two dice shows a 6, given that at least one of them shows a 6.

Many thanks in advance; what does that last sentence even mean?!
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on November 11, 2010, 05:03:55 am
A dice is known to be biased in such a way that, when it is thrown, the probability of a 6 showing is \frac{1}{4}.  This biased dice and an ordinary fair dice are thrown.  Find the probability that exactly one of the two dice shows a 6, given that at least one of them shows a 6.

Many thanks in advance; what does that last sentence even mean?!

You have to find the probability that; if together both the dices are thrown, at-least from both, 1 shows a six, and from both 1 has to show 6.

1       1         5
-- + ---   = -----
4       6         12

Is this the answer ?
Title: Re: S1 DOUBTS HERE!!!!
Post by: Deadly_king on November 11, 2010, 05:16:55 am
You have to find the probability that; if together both the dices are thrown, at-least from both, 1 shows a six, and from both 1 has to show 6.

1       1         5
-- + ---   = -----
4       6         12

Is this the answer ?

Nope........you did it wrong there dude.

The question asked at least a six form both dices but exactly one six should be obtained.

Hence probable results are :
1. 6 from biased die and any other number from unbiased die.
2. Any other number from unbiased die and 6 from unbiased die.

Probability : (1/4 x 5/6) + (3/4 x 1/6) = 1/3
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on November 11, 2010, 05:22:14 am
Nope........you did it wrong there dude.

The question asked at least a six form both dices but exactly one six should be obtained.

Hence probable results are :
1. 6 from biased die and any other number from unbiased die.
2. Any other number from unbiased die and 6 from unbiased die.

Probability : (1/4 x 5/6) + (3/4 x 1/6) = 1/3

Yeah !! :D
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ivo on November 11, 2010, 08:03:07 pm
Nope........you did it wrong there dude.

The question asked at least a six form both dices but exactly one six should be obtained.

Hence probable results are :
1. 6 from biased die and any other number from unbiased die.
2. Any other number from unbiased die and 6 from unbiased die.

Probability : (1/4 x 5/6) + (3/4 x 1/6) = 1/3

Hmm, apparently the answer is 8/9.  Any ideas?
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 11, 2010, 08:56:04 pm
got 8/9. faffing around with scanner
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 11, 2010, 09:05:48 pm
here
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on December 21, 2010, 02:30:45 pm
Instinct change ! No doubts here now, for anybody. :o
Title: Re: S1 DOUBTS HERE!!!!
Post by: vondutchLG on January 29, 2011, 10:06:29 am
A:one of the two dice shows a 6
B:at least one of them shows a 6

first find B
a tree diagram would help...........
1/4*1/6+1/4*5/6+3/4*1/6=3/8
P(B)=3/8
P(A)=1/4*5/6+3/4*1/6=1/3
P(A!B)=this means probabiltiy of A given that B
P(A)=1/3 / 3/8=8/9

hop u get it
Title: Re: S1 DOUBTS HERE!!!!
Post by: ashish on February 10, 2011, 03:22:36 am
there are 6 boys and 3 women ..

how many possible ways are there if no 2 women are standing next to each other?
ans : 151200
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 10, 2011, 01:40:34 pm
here
Title: Re: S1 DOUBTS HERE!!!!
Post by: ashish on February 11, 2011, 04:43:41 am
here

thank you sir i got it now
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saavya on February 15, 2011, 05:58:22 pm
Hello  :) im taking cie s1 and wondering if u know the way to find standard deviation on calculator , i use casio fx-991es and cant find any help on web  :-\
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on February 16, 2011, 07:55:36 am
A coin is tossed 10 times
(a) How many different sequences of heads and tails are possible.
(b) How many different sequences containing six heads and four tails are possibles.
(c) What is the probability of getting six heads and four tails.
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 16, 2011, 09:12:03 am
Hello  Smiley im taking cie s1 and wondering if u know the way to find standard deviation on calculator , i use casio fx-991es and cant find any help on web  Undecided

From memory
Shift mode stat

choose 1 or 2  variable
input data
Choose shift 4
var
Then choose sigma_n or sigma_{n-1}
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 16, 2011, 09:15:07 am
A coin is tossed 10 times
(a) How many different sequences of heads and tails are possible.
(b) How many different sequences containing six heads and four tails are possibles.
(c) What is the probability of getting six heads and four tails.
a)2^10 =1024
b)10C4 or 10C4
c)10C4/2^10
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saavya on February 17, 2011, 08:09:07 am
From memory
Shift mode stat

choose 1 or 2  variable
input data
Choose shift 4
var
Then choose sigma_n or sigma_{n-1}

Thank You !  :D
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on February 18, 2011, 03:18:56 pm
A coin is tossed 10 times
(a) How many different sequences of heads and tails are possible.
(b) How many different sequences containing six heads and four tails are possibles.
(c) What is the probability of getting six heads and four tails.
a)2^10 =1024
b)10C4 or 10C4
c)10C4/2^10
thanxx
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saavya on February 22, 2011, 04:40:22 pm
can we solve basic binomial distribution questions on calculator ?! if yes then how ??

 
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on February 22, 2011, 05:50:29 pm
can we solve basic binomial distribution questions on calculator ?! if yes then how ??

 

i think u want every thing in calculator

but for the factorial part
press shift and then press exactly below it
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saavya on February 22, 2011, 07:12:44 pm
i think u want every thing in calculator

but for the factorial part
press shift and then press exactly below it

lol ! yes  ;)
my tcher sux big time...if we ppl follow what she explains,we'll definitely be ending up with Es and Us in stats...
so why not try to save some time and do what guarantees a full mark   :)


and Thank You  :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: elemis on February 23, 2011, 11:36:42 am
lol ! yes  ;)
my tcher sux big time...if we ppl follow what she explains,we'll definitely be ending up with Es and Us in stats...
so why not try to save some time and do what guarantees a full mark   :)


and Thank You  :)

If you dont show the necessary workings you'll still land up with Es and Us. A correct answer doesnt guarantee full marks.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Saavya on February 23, 2011, 02:30:05 pm
If you dont show the necessary workings you'll still land up with Es and Us. A correct answer doesnt guarantee full marks.


the ones i asked for do. =)
Title: Re: S1 DOUBTS HERE!!!!
Post by: $H00t!N& $t@r on April 04, 2011, 08:17:14 pm
The letters of the word CONSTANTINOPLE are written on 14 cards, one on each card. The cards are shuffled and then arranged in a straight line.

How many arrangements are there where no two vowels are next to each other?

The answer is: 457228800

I'm not getting the right answer for some reason...  :-\
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 05, 2011, 05:54:08 am
The letters of the word CONSTANTINOPLE are written on 14 cards, one on each card. The cards are shuffled and then arranged in a straight line.

How many arrangements are there where no two vowels are next to each other?

The answer is: 457228800

I'm not getting the right answer for some reason...  :-\

9 consonants and 5 vowels.
Arrangement for consonants = 9!, thereby we have 10 spaces to fit in the vowels, and they can be arranged in any manner. So arrangement for these : 10C5 X 5

Multiplying all : 9! X 10C5 X 5

Title: Re: S1 DOUBTS HERE!!!!
Post by: mdwael on April 05, 2011, 12:02:47 pm
What does  " µ" symbol mean? I saw it in some questions..does it mean anything like sigma means standard deviation? are there any more weird symbols in S1 we should know about? What are the things given in the formula booklet for S1 that we shouldnt learn?
Title: Re: S1 DOUBTS HERE!!!!
Post by: Alpha on April 05, 2011, 12:08:17 pm
What does  " µ" symbol mean? I saw it in some questions..does it mean anything like sigma means standard deviation? are there any more weird symbols in S1 we should know about? What are the things given in the formula booklet for S1 that we shouldnt learn?

"µ" stands for the Greek letter, moew. Equivalent of the mean. You will use it in distributions most often.
Title: Re: S1 DOUBTS HERE!!!!
Post by: mdwael on April 07, 2011, 12:55:31 pm
I have attached a question can someone try solving it?
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 11, 2011, 05:45:01 pm
Can someone please solve for me Question 3 in May 2009 with steps?
Title: Re: S1 DOUBTS HERE!!!!
Post by: Aadeez || Zafar on April 11, 2011, 06:52:08 pm
Can someone please solve for me Question 3 in May 2009 with steps?
(i)
P(0 buses) = (1-0.16)11
P(1 bus) = 11C1(0.16)(1-0.16)10
P(2 buses) = 11C2(0.16)2(1-0.16)9

where X is number of buses passed

so

P(X<3)= P(0 Busus)+P(1 Buses)+P(2 buses)

(ii)

USE normal distribution


mean = np
        = 125(1-(0.16+0.2))
        = 125 (0.64)
       = 80
variance = npq
            = 125 (0.64)(1-0.64)
             = 28.8
let X be number of car passed

so

p(X>73)
= 1-P(X<=73)
=1 - ?((73-80)/root(28.8)
=1-?(-1.304)
=1-(1-?(1.304))
=1-1+?(1.304)
= ?(1.304)

use normal distribution tabel to get the value of ?(1.304)
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 11, 2011, 07:28:14 pm
(i)
P(0 buses) = (1-0.16)11
P(1 bus) = 11C1(0.16)(1-0.16)10
P(2 buses) = 11C2(0.16)2(1-0.16)9

where X is number of buses passed

so

P(X<3)= P(0 Busus)+P(1 Buses)+P(2 buses)

(ii)

USE normal distribution


mean = np
        = 125(1-(0.16+0.2))
        = 125 (0.64)
       = 80
variance = npq
            = 125 (0.64)(1-0.64)
             = 28.8
let X be number of car passed

so

p(X>73)
= 1-P(X<=73)
=1 - ?((73-80)/root(28.8)
=1-?(-1.304)
=1-(1-?(1.304))
=1-1+?(1.304)
= ?(1.304)

use normal distribution tabel to get the value of ?(1.304)

I think you just solved a wrong question?
My question was about histograms.

Here' the link to the paper:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20June/6683%20June%202009.pdf

I want Question 3 please! :)

& if you don't mind can you please explain to me Question 3e of January 2009 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20Jan/S1%202009-01.pdf

Thank you! :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Aadeez || Zafar on April 11, 2011, 07:29:15 pm
ohhh!
ur edexcel studemt srry i thought u r a cie student
Title: Re: S1 DOUBTS HERE!!!!
Post by: Aadeez || Zafar on April 11, 2011, 07:34:09 pm
I think you just solved a wrong question?
My question was about histograms.

Here' the link to the paper:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20June/6683%20June%202009.pdf

I want Question 3 please! :)

& if you don't mind can you please explain to me Question 3e of January 2009 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20Jan/S1%202009-01.pdf

Thank you! :)
widht would be::

  3*2/6 = 1 cm
and height is :

10*9/15 = 6
so 6/1 = 6 cm

SIMPLE
Title: Re: S1 DOUBTS HERE!!!!
Post by: Aadeez || Zafar on April 11, 2011, 07:45:33 pm
I think you just solved a wrong question?
My question was about histograms.

Here' the link to the paper:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20June/6683%20June%202009.pdf

I want Question 3 please! :)

& if you don't mind can you please explain to me Question 3e of January 2009 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20Jan/S1%202009-01.pdf

Thank you! :)

Var(X) = Sigma(xi2pi)-(mmean)2
= = Sigma(xi2pi)-(xipi)2
=[02(0.4)+12(0.3)+22(0.2)+32(0.1)]-[(0(0.4)+(1(0.3)+(2(0.2)+(3(0.1)/4]2
=[0(0.4)+1(0.3)+4(0.2)+9(0.1)]-[(0+0.3+0.4+0.3)]2
=[0+0.3+0.8+0.9]-(1)2
=2-1
=1
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 11, 2011, 07:50:50 pm
widht would be::

  3*2/6 = 1 cm
and height is :

10*9/15 = 6
so 6/1 = 6 cm

SIMPLE


Can you please explain to me what those numbers mean, what does the 3, 2, 6, 10, 9 and 15 stand for? :/

I'm sorry for the trouble, but this lesson has been annoying me since the IG's!

& again, you solved the wrong question, I wanted part e not d! ;)
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 11, 2011, 10:59:47 pm
Okay, I've compiled my questions here in this post to make it easier! :)

1. Question 3 of June 2009 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20June/6683%20June%202009.pdf

2. Question 3e of January 2009 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20Jan/S1%202009-01.pdf

3. Question 7c of June 2008 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20June/S1%202008-june-qp.pdf

4. Questions 6b and c of January 2008 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20Jan/6683_01_que_20080115.pdf

With explanation please, I have the marking scheme, so I know the answers, but I can't understand the working/how to do it! :/

Thanks alot! :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 12, 2011, 09:38:02 am

Can you please explain to me what those numbers mean, what does the 3, 2, 6, 10, 9 and 15 stand for? :/

I'm sorry for the trouble, but this lesson has been annoying me since the IG's!

& again, you solved the wrong question, I wanted part e not d! ;)


Formula for

(i) frequency density (height) :

    frequency  
= ------------
    class width

(ii) class width (interval) :

        frequency
= ------------------
     frequency density


Now for your question :

3 (a)

x = 10 - 15 (9.5 - 15.5); frequency = 15.

class width = (15.5 - 9.5) = 6. This is taken in histogram as 2 cm.
For 16 - 19, width is (19.5 - 16.5) = 3.

In the histogram, the width of the 16 - 18 class will be :  (3 X 2)/6 = 1



(b)

Height (or frequency density) = (15 / 6) = 2.5. This is taken in histogram as 5 cm.
For 16 - 19, height is (9 / 3) = 3.

In the histogram, the height of the 16 - 18 class will be : (3 X 5)/2.5 = 6

Tell me if you still didn't get.

Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 12, 2011, 12:40:46 pm
Formula for

(i) frequency density (height) :

    frequency  
= ------------
    class width

(ii) class width (interval) :

        frequency
= ------------------
     frequency density


Now for your question :

3 (a)

x = 10 - 15 (9.5 - 15.5); frequency = 15.

class width = (15.5 - 9.5) = 6. This is taken in histogram as 2 cm.
For 16 - 19, width is (19.5 - 16.5) = 3.

In the histogram, the width of the 16 - 18 class will be :  (3 X 2)/6 = 1



(b)

Height (or frequency density) = (15 / 6) = 2.5. This is taken in histogram as 5 cm.
For 16 - 19, height is (9 / 3) = 3.

In the histogram, the height of the 16 - 18 class will be : (3 X 5)/2.5 = 6

Tell me if you still didn't get.



Thanks a lot! :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Alpha on April 12, 2011, 05:56:55 pm
1. Question 3 of June 2009

Frequency density= Freq/ Class width
The freq. density will be the height of your histogram in case of unequal class widths.

x :10 – 15
Frequency= 15
Class width= 15 - 10 = 5

Frequency density= 15/5 = 3

Now, use proportions.

Class width,  5 : 2
Height, 3 : 5

For 16 – 18:

Class width=18 - 16 = 2
On histogram -> 2/5*2= 1/5

Frequency density=9/2 = 4.5
On histogram ->(5/3)*(9/2) = 15/2 = 7.5


I don't find the MS from your link... so, please check it.




Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 12, 2011, 07:25:32 pm
1. Question 3 of June 2009

Frequency density= Freq/ Class width
The freq. density will be the height of your histogram in case of unequal class widths.

x :10 – 15
Frequency= 15
Class width= 15 - 10 = 5

Frequency density= 15/5 = 3

Now, use proportions.

Class width,  5 : 2
Height, 3 : 5

For 16 – 18:

Class width=18 - 16 = 2
On histogram -> 2/5*2= 1/5

Frequency density=9/2 = 4.5
On histogram ->(5/3)*(9/2) = 15/2 = 7.5


I don't find the MS from your link... so, please check it.






I'm sorry, your answers are wrong, check Fidato's post above for the right answer.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 13, 2011, 11:10:52 am
1. Question 3 of June 2009

Frequency density= Freq/ Class width
The freq. density will be the height of your histogram in case of unequal class widths.

x :10 – 15
Frequency= 15
Class width= 15 - 10 = 5

Frequency density= 15/5 = 3

Now, use proportions.

Class width,  5 : 2
Height, 3 : 5

For 16 – 18:

Class width=18 - 16 = 2
On histogram -> 2/5*2= 1/5

Frequency density=9/2 = 4.5
On histogram ->(5/3)*(9/2) = 15/2 = 7.5


I don't find the MS from your link... so, please check it.

Alpa, there you went wrong. Check the intervals before 16 - 18. They were 10 - 15, so in order to built a histogram, you need to amend the values to make them continuous (so you subtract 0.5 from the lower limit and add 0.5 to the upper limit).

Like take two class intervals, (10 - 15) and (16 - 18). There's gap of 1 between 15 and 16, so how can you make a histogram ?
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 13, 2011, 11:14:18 am
Doing the rest.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 13, 2011, 11:52:01 am
Okay, I've compiled my questions here in this post to make it easier! :)

Here they follow.

Quote
1. Question 3 of June 2009 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20June/6683%20June%202009.pdf

Done.

Quote
2. Question 3e of January 2009 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2009%20Jan/S1%202009-01.pdf

After 3 games Rohit has scored 6.
2 games are left and he has to get 4 points or more to win the prize.

List all the outcomes of the points he can get (see the image below).
You can see that there are 16 possible outcomes and six of which fetch him 4 points or more.
You know that :
P(0) = 0.4
P(1) = 0.3
P(2) = 0.2
P(3) = 0.1

So to win a price he should get points with the outcomes as follows (as circled in image).

{ (1,3) (2,2) (2,3) (3,1)(3,2) (3,3) }

Multiply and add the probabilities :

(0.3 X 0.1) + (0.2 X 0.2) + (0.2 X 0.1) + (0.1 X 0.3) + (0.1 X 0.2) + (0.1 X 0.1)

= 0.03 + 0.04 + 0.02 + 0.03 + 0.02 + 0.01
= 0.15
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 13, 2011, 12:45:20 pm
Quote
3. Question 7c of June 2008 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20June/S1%202008-june-qp.pdf

(7) (c)

For this you need to find out the probability that the bag weighs more than 53 kg.


(a)

More than 53, so (53 + 0.5 = 53.5)

        53.5 - 50
Z =  ------------
             2
= si (1.75)
= 0.9599

Now, it's greater then 53, so :

   1 - { si (1.75) }
= 1 - 0.959
= 0.0401


(c)

2 bags greater than 53 kg and 1 less than 53 kg .

Probability that any bag is greater then 53 kg = 0.0401
and
Probability that it is less then 53 kg = 0.959

So :

3C2 X (0.401)2 X (0.959)
= 0.004630586
= 0.0046
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 13, 2011, 12:49:10 pm
Quote
4. Questions 6b and c of January 2008 on this link:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20Jan/6683_01_que_20080115.pdf

(6) (b)

Weights between 190 and 210 are 60 %.

Now 60 % is equal to 0.6 of the probability right. So find out the value of si (0.6) which is equal to 0.7257 .

Now you know the formula :

                X - mean
Z =         -------------
          standard deviation

Let standard deviation be s.
So :

 210 - 200            190 - 200   
------------    -     ------------ = 0.7257
       s                         s

10 - (-10)
----------- = 0.7257
       s

20 = 0.7257s
s = 20/(0.7257)
standard deviation = 27.55959763 (or 27.56)


(c)

Use the same formula of normal distribution.
If you will use the original value of standard deviation (that is 27.55959763 and not 27.56), you will be benefited.

  180 - 200
---------------
27.55959763

= si (-0.7257)
= 1 - { si (0.726) }
= 1 - 0.766
= 0.234

So 0.234 is the probability that the customer will complain.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 13, 2011, 12:50:04 pm
Quote
With explanation please, I have the marking scheme, so I know the answers, but I can't understand the working/how to do it! :/
Thanks alot! :)

Can you please provide all 4 marking schemes please ? Here itself.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 13, 2011, 03:45:52 pm
What Master_Key told is correct. Sorry it just got deleted, while I was playing with my slow internet around. :D

Firstly, don't forget to add (+0.5) if you are finding probability of a greater than number like in your 3rd question it was more than 53 kg, otherwise you may get a penalty (loss of marks) - I don't know whether the same is practised in ED-EXCEL or not.

Lastly, if you don't want to forget to keep in (+0.5), just apply the formula without adding (+0.5):

1 - { si (<=X) }
Title: Re: S1 DOUBTS HERE!!!!
Post by: Alpha on April 13, 2011, 05:26:33 pm
I'm sorry, your answers are wrong, check Fidato's post above for the right answer.

Apologies. I wasn't in my right state of mind. -.-

Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 13, 2011, 06:53:53 pm
Here they follow.

Done.

After 3 games Rohit has scored 6.
2 games are left and he has to get 4 points or more to win the prize.

List all the outcomes of the points he can get (see the image below).
You can see that there are 16 possible outcomes and six of which fetch him 4 points or more.
You know that :
P(0) = 0.4
P(1) = 0.3
P(2) = 0.2
P(3) = 0.1

So to win a price he should get points with the outcomes as follows (as circled in image).

{ (1,3) (2,2) (2,3) (3,1)(3,2) (3,3) }

Multiply and add the probabilities :

(0.3 X 0.1) + (0.2 X 0.2) + (0.2 X 0.1) + (0.1 X 0.3) + (0.1 X 0.2) + (0.1 X 0.1)

= 0.03 + 0.04 + 0.02 + 0.03 + 0.02 + 0.01
= 0.15

This one's right and I understood it, thank you! :)

I'm sorry, the link for the marking scheme for this paper is not opening now! :/
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 13, 2011, 06:54:58 pm
(7) (c)

For this you need to find out the probability that the bag weighs more than 53 kg.


(a)

More than 53, so (53 + 0.5 = 53.5)

        53.5 - 50
Z =  ------------
             2
= si (1.75)
= 0.9599

Now, it's greater then 53, so :

   1 - { si (1.75) }
= 1 - 0.959
= 0.0401


(c)

2 bags greater than 53 kg and 1 less than 53 kg .

Probability that any bag is greater then 53 kg = 0.0401
and
Probability that it is less then 53 kg = 0.959

So :

3C2 X (0.401)2 X (0.959)
= 0.004630586
= 0.0046


The answer is wrong, the mark scheme is here: http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20June/S1%20june%2008%20ms.pdf
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 13, 2011, 06:55:40 pm
(6) (b)

Weights between 190 and 210 are 60 %.

Now 60 % is equal to 0.6 of the probability right. So find out the value of si (0.6) which is equal to 0.7257 .

Now you know the formula :

                X - mean
Z =         -------------
          standard deviation

Let standard deviation be s.
So :

 210 - 200            190 - 200   
------------    -     ------------ = 0.7257
       s                         s

10 - (-10)
----------- = 0.7257
       s

20 = 0.7257s
s = 20/(0.7257)
standard deviation = 27.55959763 (or 27.56)


(c)

Use the same formula of normal distribution.
If you will use the original value of standard deviation (that is 27.55959763 and not 27.56), you will be benefited.

  180 - 200
---------------
27.55959763

= si (-0.7257)
= 1 - { si (0.726) }
= 1 - 0.766
= 0.234

So 0.234 is the probability that the customer will complain.

The answer is also wrong, the mark scheme is here:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20Jan/6683_01_rms_20080306.pdf
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on April 13, 2011, 06:56:54 pm
Apologies. I wasn't in my right state of mind. -.-



No problem! :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 14, 2011, 07:07:50 am
The answer is wrong, the mark scheme is here: http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20June/S1%20june%2008%20ms.pdf

In (a) there was a mistake so part (c) was influenced.

I took +0.5, so things happened.

You just find out the value of Z without adding (0.5) to 53, because at the end you have to subtract it from 1 anyhow.

I hope you understood and will do the (c) part yourself.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on April 14, 2011, 07:28:00 am
The answer is also wrong, the mark scheme is here:
http://www.xtremepapers.net/Edexcel/Advanced%20Level/Mathematics/2008%20Jan/6683_01_rms_20080306.pdf

Oh ! I now realised that I had taken si (0.6) and not si-1 (0.6).

Anyways I think you got that (+-) method that they have used. Actually P(X<210) = 0.8 so they have taken si-1 ( 0.8 ) and nothing else.
Title: Re: S1 DOUBTS HERE!!!!
Post by: thecandydoll on April 17, 2011, 03:51:20 am
Hey
i just dont permutation and combinations.
any notes?
or what if i skip this question,I am fine with the rest of the question.
thanks :(
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on April 17, 2011, 09:04:28 am
Hey
i just dont permutation and combinations.
any notes?
or what if i skip this question,I am fine with the rest of the question.
thanks :(
but it is one of the scoring part of the paper
we just have to understand the condition of the question and do it
Title: Re: S1 DOUBTS HERE!!!!
Post by: Aadeez || Zafar on April 17, 2011, 09:05:37 am
Hey
i just dont permutation and combinations.
any notes?
or what if i skip this question,I am fine with the rest of the question.
thanks :(
see the video  of combination and permutation in KHAN ACADEMEY

would help u

i and my frnds had the sme problem but is solved now
Title: Re: S1 DOUBTS HERE!!!!
Post by: thecandydoll on April 17, 2011, 11:41:00 am
i tried... :(
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on April 17, 2011, 12:34:27 pm
i tried... :(

try try and you will succeed
Title: Re: S1 DOUBTS HERE!!!!
Post by: narnia on April 21, 2011, 09:00:28 pm
a fair dice is thrown once. what is the probability that the score is greatr than 3 or a prime number or both?
i added 3/6 + 3/6 + ( 3/6*3/6) , my ans being 5/4 wherews ans given is 5/6 =s
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on April 22, 2011, 12:19:51 pm
a fair dice is thrown once. what is the probability that the score is greatr than 3 or a prime number or both?
i added 3/6 + 3/6 + ( 3/6*3/6) , my ans being 5/4 wherews ans given is 5/6 =s

(x>3)=4,5,6
p of (x>3)=3/6
(x a prime number)= 2,3,5,   
p of (x a prime number)
So both =2,3,5 and 4,5,6

5 is repeated so (2,3,4,5,6)=p of both 5/6
the Question was to confuse you .
Title: Re: S1 DOUBTS HERE!!!!
Post by: ashish on April 24, 2011, 07:29:03 am
rex has an old car. the probability that he is able to start the car on a rainy day is 0.2 and the probability that he is able to start it on a fine day is 0.6 . if the weather is either fine or rainy, and probability the weather is fine is p, the find in terms of p
1) the probability that he is unable to start the car on a day
2) the conditional probability that a day is fine and he is unable to start the car?

can someone solve this question please ???
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on April 24, 2011, 08:57:01 am
One mo
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on April 24, 2011, 09:09:59 am
prob solved in attachment
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on April 24, 2011, 09:38:11 am
prob solved in attachment
thanx Mr. Paul
Title: Re: S1 DOUBTS HERE!!!!
Post by: astarmathsandphysics on April 24, 2011, 10:31:46 pm
No probs
Title: Re: S1 DOUBTS HERE!!!!
Post by: Malak on April 30, 2011, 04:02:50 pm
Need help with this question

Part (e) to find median
I know we use interpolation but i am confused with the values to use for the upper/lower cumulative frequency..
thx

This is S1 Q5 from 2007 Jun
Title: Re: S1 DOUBTS HERE!!!!
Post by: mdwael on May 01, 2011, 11:12:58 am
Need help with this question

Part (e) to find median
I know we use interpolation but i am confused with the values to use for the upper/lower cumulative frequency..
thx

This is S1 Q5 from 2007 Jun


First of all make a cumulative frequency table.

you have a total of 100. Thus median should be the 50th entry.. so when you make the cf you will find the the 50th tab lies in 14-18 class and Cf is 26-50.. here it is not neccessary to do interpolation because 50 is the last one in the class so you can directly pick median of t is 18 seconds. but you can still do interpolation to check your answer.


    (X - 14) / 18-14 = 50-26 / 50 -26

X-14 / 4 = 1

X-14 = 4

X = 14 + 4 = 18


In the same manner u find the quartiles... since the  total frequency is 100 so lower quartile is 100/4 = 25 and upper is 100*3/4 = 75th entry
Title: Re: S1 DOUBTS HERE!!!!
Post by: mdwael on May 01, 2011, 11:22:29 am
I have a question regarding Normal Distribution..

I understand how to get and find probabilities but how do you find the mean and standard deviation when the lower quartile and upper quaritle are given? like in this question..

(http://)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Aadeez || Zafar on May 01, 2011, 02:18:28 pm
in normal distribution,
median =means

and so median= (LQ+UQ)/2

using mean value find s.d
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on May 03, 2011, 10:31:04 am
in normal distribution,
median =means

and so median= (LQ+UQ)/2

using mean value find s.d

BOLD - How can this be possible ?

Take upper quartile as 75 % (probability of 0.75) OR lower quartile as 25 % (probability of 0.25). Though I recommend you to take 0.75 because for LOWER QUARTILE (0.25) you have to do a bit of more subtraction which will be confusing.
Title: Re: S1 DOUBTS HERE!!!!
Post by: xMilishax on May 17, 2011, 02:05:59 pm
Can someone help me solve:
May 2010 Q7 Part (b)?

I'm kinda confused with Normal distribution.

Thanks.  :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on May 17, 2011, 02:12:07 pm
Quote
Can someone help me solve:
May 2010 Q7 Part (b)?

I'm kinda confused with Normal distribution.

Thanks.  :)

Variant ?
Title: Re: S1 DOUBTS HERE!!!!
Post by: xMilishax on May 17, 2011, 02:25:24 pm
Variant ?

Variant 1
Title: Re: S1 DOUBTS HERE!!!!
Post by: Arthur Bon Zavi on May 17, 2011, 04:02:26 pm
Peter will continue UNTIL he has got an answer wrong. It will then not matter him getting answer by being helped.

Working in attachment :
Title: Re: S1 DOUBTS HERE!!!!
Post by: mdwael on May 18, 2011, 06:38:42 pm
Can someone suggerst me really hard edexel S1 past papers for practice?
Title: Re: S1 DOUBTS HERE!!!!
Post by: igext on May 19, 2011, 10:33:45 am
Hey, I do Edexcel S1, please post all your doubts here!!!

hello
i just have one question
June 2008 Q7(c)
question about normal dist.
I dont get why they are multiplying by 3?
Thank you loads in advance.
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on May 19, 2011, 01:51:59 pm
Guys, I need help in those theoretical questions that they ask, how do you 'apply' your knowledge of the subject there?
Like is there any rule sort of thing that we need to know, for example in mechanics by assuming that the string is inextensible, the acceleration is the same, so is there anything similar to that in S1?
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on May 19, 2011, 02:28:58 pm
Guys try solving Solomon paper L and someone tell me why did they take the value of n as 121 to find the Quartiles and not 120 in Q7a.

 http://www.freeexampapers.com/past_papers.php?l=Past_Papers%2FA+Level%2FMaths%2FEdexcel%2FS1%2FSolomon/
Title: Re: S1 DOUBTS HERE!!!!
Post by: mdwael on May 19, 2011, 06:01:28 pm
hello
i just have one question
June 2008 Q7(c)
question about normal dist.
I dont get why they are multiplying by 3?
Thank you loads in advance.

Because you are picking 3 bags at any order. so you can go like this. let the bag which is less than 53 be A and if its more than 53 be B.
They want 2 Bs and 1 A,

If they are chosen at random the arrangement can come

 B B A

 B A B

 A B B

so there are 3 ways of getting 2 bags which weigh more than 53 and one bag which weighs less. so you multiply the probabilities and then add them or just find the probability once and multiply it by 3. Hope this helps.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on May 19, 2011, 06:11:41 pm
ok...i have my s1 exam coming(i mean we all do :P)...so i have a few doubts.......its from may/june 2007 qns 1....i dont get it at all
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on May 19, 2011, 06:45:18 pm
ok...i have my s1 exam coming(i mean we all do :P)...so i have a few doubts.......its from may/june 2007 qns 1....i dont get it at all

For part a)
r=Sxy/?(SxxSyy) = -808.917/?(113573 x 8.657) = -0.816 (3sf)
and by the way, the formula is given in the formula booklet.

b) Since the product moment correlation coefficient is a negative value, then this means that as one value increases, the other value decreases, so in this case, the houses become cheaper as they become further away from the station.

c) The product moment correlation coefficient is not affected by coding i.e. if you add, subtract, multiply or divide the original data for coding, it'll not change, so it's value is the same.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on May 19, 2011, 06:49:09 pm
wait.....is this page for edexcel paper???....because im doing CIE!!!opsie :-[
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 19, 2011, 06:55:45 pm
ok...i have my s1 exam coming(i mean we all do :P)...so i have a few doubts.......its from may/june 2007 qns 1....i dont get it at all

Let x = t - 35

Therefore, Mean = -15/12 = -1.25
However, this is the mean for (t-35)

The mean for t = -1.25 + 35 = 33.75 ~ 33.8

The s.d for x (i.e t-35) is the same as the s.d for t

So, S.d = sqrt(Sum(x_i^2)/12 - (mean^2(for t-35)

= sqrt((82.23/12)-(-1.25)^2 = 2.3
Title: Re: S1 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on May 19, 2011, 06:59:02 pm
thanks alot!!!
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on May 19, 2011, 07:00:58 pm
Guys try solving Solomon paper L and someone tell me why did they take the value of n as 121 to find the Quartiles and not 120 in Q7a.

 http://www.freeexampapers.com/past_papers.php?l=Past_Papers%2FA+Level%2FMaths%2FEdexcel%2FS1%2FSolomon/

& Solomon paper J, why are they taking the value of n as 56 instead of 55 in Q1a?
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on May 19, 2011, 07:01:42 pm
wait.....is this page for edexcel paper???....because im doing CIE!!!opsie :-[

I thought you're Edexcel because the S1 paper is actually tomorrow.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on May 19, 2011, 07:05:38 pm
I thought you're Edexcel because the S1 paper is actually tomorrow.
no im CIE.......its ok.......BEST OF LUCK for ur s1 exam tomorrow!!!ALL of u ;)
Title: Re: S1 DOUBTS HERE!!!!
Post by: daas on May 19, 2011, 07:56:36 pm
 hi,

1 doubt...perhaps the last one
may/jun 2010 Q3 part e) ???
Title: Re: S1 DOUBTS HERE!!!!
Post by: mdwael on May 19, 2011, 08:11:47 pm
okay I have something which I want to make clear of.  When you code data.. Product moment correlation is not affected, Variance and standard deviation are only affected when you multiply and divide and Mean is affected by everything. Am I right?
Title: Re: S1 DOUBTS HERE!!!!
Post by: xMilishax on May 19, 2011, 08:57:05 pm
Can someone please explain Q7(a) in Jan 2011 S1 paper?

Thanks.  :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: xMilishax on May 19, 2011, 09:22:46 pm
I got it. LOL  :P
Title: Re: S1 DOUBTS HERE!!!!
Post by: Master_Key on May 24, 2011, 02:04:19 pm
CIE

9709_s10_qp_62

Q 7 (ii).

I just want to know any short method, i have got the answer but with a way too long method.
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 24, 2011, 02:37:33 pm
CIE

9709_s10_qp_62

Q 7 (ii).

I just want to know any short method, i have got the answer but with a way too long method.

as the markscheme suggests, its simple. 

The no. of ways the pink card is not next to the green card = Total no. of ways - (the no. of ways the green card and the pink are together)

The no. of ways the pink and green are together...
There is a very neat trick to find this, it's in there in the CIE S1 book
U consider the 2 cards as a unit, and permute them with the other 7

Like this [pink, green] + 7 others... = total 8 (regarding the pink, green as one unit)
 
The permutation = 2*8!

Subtract this from 9! and u have ur answer

9!-(2*8!)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Master_Key on May 24, 2011, 02:41:04 pm
as the markscheme suggests, its simple.  

The no. of ways the pink card is not next to the green card = Total no. of ways - (the no. of ways the green card and the pink are together)

The no. of ways the pink and green are together...
There is a very neat trick to find this, it's in there in the CIE S1 book
U consider the 2 cards as a unit, and permute them with the other 7

Like this [pink, green] + 7 others... = total 8 (regarding the pink, green as one unit)
 
The permutation = 2*8!

Subtract this from 9! and u have ur answer

9!-(2*8!)

Thank you. So for combinations also I think this would be easier. +rep(I have to wait 114 minutes)
Title: Re: S1 DOUBTS HERE!!!!
Post by: SkyPilotage on May 24, 2011, 05:36:01 pm
Do we need to know the 52 cards pack!?
Do we need to know how to derive the formulas of vairance and standard deviations in sets of date or binomial distributions or why?!?!
Thanks...
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 24, 2011, 07:19:56 pm
Do we need to know the 52 cards pack!?
Do we need to know how to derive the formulas of vairance and standard deviations in sets of date or binomial distributions or why?!?!
Thanks...

52 pack cards - yes. (No jokers ofcourse)

Derive the formulas for variance and s.d? Nah
Title: Re: S1 DOUBTS HERE!!!!
Post by: SkyPilotage on May 24, 2011, 07:35:55 pm
52 pack cards - yes. (No jokers ofcourse)

Derive the formulas for variance and s.d? Nah
can you tell me the 52 card pack?
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 24, 2011, 07:39:05 pm
can you tell me the 52 card pack?

Erm, ok sure. 52 cards. 26 red and 26 black. four As, four 2s, four 3s, four 4s................four 10's, four jacks, four queens, four kings.

13 spades, 13 hearts, 13 diamonds and 13 clubs.

Find attached image. Source : wiki
Title: Re: S1 DOUBTS HERE!!!!
Post by: dj_dead on May 25, 2011, 08:06:39 am
june 2008 paper 6 q5 part ii


when we get phi(t) = 0.7389
then how come the next step is
phi (t) = phi (0.64)


where did 0.64 come from? =S
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on May 25, 2011, 08:44:24 am
june 2008 paper 6 q5 part ii


when we get phi(t) = 0.7389
then how come the next step is
phi (t) = phi (0.64)


where did 0.64 come from? =S
I got that by the method given bellow

Take the medians of the time spent intervals
i.e. :- 0.3, 0.8, 1.55, 2.55, 3.8
now use the formula sigma fx
                            --------
                             sigma f
sigma fx = 3.3+12+27.9+76.5+79.8 = 199.5
sigma f = 11+15+18+30+21=95

:. 199.5/95=2.1
the mean is 2.1 hours
hope it helps
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 25, 2011, 09:18:33 am
june 2008 paper 6 q5 part ii


when we get phi(t) = 0.7389
then how come the next step is
phi (t) = phi (0.64)


where did 0.64 come from? =S

I guess the question/question paper you stated isn't the question you are confused about.

Anyway, i dont know the q, but i guess i understand ur doubt.

phi(t) = 0.7389
Meaning, for which value of 't' is the area 0.7389. For this u gotta look at the normal distribution table. You'll find it in the CIE S1 book
and the syl.

I've attached the part of the table where I found 0.7389. If you look closely, you'll see that cell (red) is in the 6th column (starting from column 'z') and the 7th row (starting from 0.0). 0.60 + 0.04 = 0.64,
Title: Re: S1 DOUBTS HERE!!!!
Post by: melony on May 25, 2011, 05:56:01 pm
For something like (x>35) how do you know when to use     x.5-meuow/s.d. how do you know its x.5 and not x, is there a pattern!! agghhh!! im panicking before my s1 exam!!  :'( help someone!! like for 62/ON/10 qs 6 (iii) i had no clue which one to use!! :/!!  ??? :(
Title: Re: S1 DOUBTS HERE!!!!
Post by: SkyPilotage on May 25, 2011, 06:00:36 pm
For something like (x>35) how do you know when to use     x.5-meuow/s.d. how do you know its x.5 and not x, is there a pattern!! agghhh!! im panicking before my s1 exam!!  :'( help someone!! like for 62/ON/10 qs 6 (iii) i had no clue which one to use!! :/!!  ??? :(
Listen: You use the .5 thing (called Continuity correction) When you use Normal Approximation instead of binomiall.....For Example:
If its > then its 35.5
IF its < then its 34.5
If its > or equal its 34.5
If its < or equal its 35.5
Title: Re: S1 DOUBTS HERE!!!!
Post by: melony on May 25, 2011, 06:12:29 pm
so for like 7(i) 63/ON/10 you wouldn't use it because it cant be done binomially?
thanks sooooo much you're a life saver!! - that clears that topic up for me! god bless u!!
Title: Re: S1 DOUBTS HERE!!!!
Post by: SkyPilotage on May 25, 2011, 06:31:01 pm
so for like 7(i) 63/ON/10 you wouldn't use it because it cant be done binomially?
thanks sooooo much you're a life saver!! - that clears that topic up for me! god bless u!!
In question 7 i) its already Normal distribution so you dont have to worry abt the C.C (0.5 thing)
I will give you a simple explanation...
If they ask about the prob. of 3 trials from 5 does this event X occur? You would use the binomial as 5C3 x ...x....
But if they ask you the prob of greater than 156 of event X occurs from 200... You could not possibly do 200C156 x...x... + 200C157 x...x... +.... Till 200C200
So thats why we use the continuity correction to approximate it as a Normal Distribution....So tht It would be much easier..So The Continuity correction here would be 15_._ You tell me  :D
Title: Re: S1 DOUBTS HERE!!!!
Post by: melony on May 25, 2011, 06:57:07 pm
156.5!!!!!!!  ;D
thank you so much! good luck tomorow!!   :)
Title: Re: S1 DOUBTS HERE!!!!
Post by: SkyPilotage on May 25, 2011, 07:00:33 pm
156.5!!!!!!!  ;D
thank you so much! good luck tomorow!!   :)
You are most welcome .. You tooo :D
By the way How are you in Permutations and Combinations??
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 25, 2011, 07:10:35 pm
Good luck for 2morrow guyz.
Title: Re: S1 DOUBTS HERE!!!!
Post by: melony on May 25, 2011, 07:14:16 pm
Quote
You are most welcome .. You tooo
By the way How are you in Permutations and Combinations??

Not too bad, but most of the times i just get lucky, everyone, i mean EVERYONE in our class can do them but are always unsure of the answer being right, i guess it's the same with everyone else from what i've heard
Title: Re: S1 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 25, 2011, 07:19:00 pm
Not too bad, but most of the times i just get lucky, everyone, i mean EVERYONE in our class can do them but are always unsure of the answer being right, i guess it's the same with everyone else from what i've heard

True, very true. Always unsure of the answer..
*sighs* , let's just hope tomorrow's paper is easy.
Title: Re: S1 DOUBTS HERE!!!!
Post by: SkyPilotage on May 25, 2011, 07:21:45 pm
Not too bad, but most of the times i just get lucky, everyone, i mean EVERYONE in our class can do them but are always unsure of the answer being right, i guess it's the same with everyone else from what i've heard
Well My problems are all In permutations and combinations as they started to get HArd from 2009-2010  :'(... I hope it comes easy tmrw... Best OF luck for all Of uss!!  ;)
Title: Re: S1 DOUBTS HERE!!!!
Post by: SkyPilotage on May 25, 2011, 07:37:40 pm
June 2010 Variant 63 question 4 II)
Can some one plzzz explain the third way in the mark scheme???
Title: Re: S1 DOUBTS HERE!!!!
Post by: melony on May 25, 2011, 08:12:06 pm
Im not sure but this is how i understood it, this is the first time im looking at it

SO the first three colas are next to each other, [CCC]

lets just let that be one big C, green tea = G, oranje juice = J

there are only three different places we can place the G:

1) G C G J J    2) G C J G J    3) G C J J G

hence the 3

note that the Gs can not be moved the only thing we can move is C J J hence 3! = 4x3/2

therefore 3x3!=18 or as the mark sceme 3x(4x3/2)

hope i helped  ;), good luck everyone im out for the night!
Title: Re: S1 DOUBTS HERE!!!!
Post by: SkyPilotage on May 25, 2011, 08:25:11 pm
Im not sure but this is how i understood it, this is the first time im looking at it

SO the first three colas are next to each other, [CCC]

lets just let that be one big C, green tea = G, oranje juice = J

there are only three different places we can place the G:

1) G C G J J    2) G C J G J    3) G C J J G

hence the 3

note that the Gs can not be moved the only thing we can move is C J J hence 3! = 4x3/2

therefore 3x3!=18 or as the mark sceme 3x(4x3/2)

hope i helped  ;), good luck everyone im out for the night!
By the way Remember! YOu cannOT do 3! only There is a repeated term which is the 2 JJ so It must be 3!/2....Couldnt the G be put 2nd and last? so It would have more than 3 laces to be moved to..Its infact 6! SO its actually 6x3!/2....But what I dont get is why they Did 4x3/2 ?!?!
Title: Re: S1 DOUBTS HERE!!!!
Post by: dj_dead on May 25, 2011, 08:40:12 pm
I guess the question/question paper you stated isn't the question you are confused about.

Anyway, i dont know the q, but i guess i understand ur doubt.

phi(t) = 0.7389
Meaning, for which value of 't' is the area 0.7389. For this u gotta look at the normal distribution table. You'll find it in the CIE S1 book
and the syl.

I've attached the part of the table where I found 0.7389. If you look closely, you'll see that cell (red) is in the 6th column (starting from column 'z') and the 7th row (starting from 0.0). 0.60 + 0.04 = 0.64,



ohhhhhh so DATS how u look at it...i ws lookin at it the other way round.....thankuu soooo veryyyy muchhh =D life saver i tel u :) all d bst wid ur papers bro !
Title: Re: S1 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on May 25, 2011, 11:00:05 pm
can someone pls explain qns 3 p62 oct/nov 2010 CIE!
Title: Re: S1 DOUBTS HERE!!!!
Post by: ........ on May 26, 2011, 12:55:05 am
can someone pls explain qns 3 p62 oct/nov 2010 CIE!


See the attachment below.

Since this is a conditional probability you find out the probability of getting a 12.

If the spinner is thrown on a even side
then there are 4 ways 12 can come.
and the probability of a spinner landing on 12 would 2/5.
So here is Probability of getting a 12 if the spinner lands on the even side
2/5 * 4/36

similarly you do this for the spinner landing on the odd side
which would be 3/5 * 1/36

Now it says it lands on a even side so the fraction should look like this
2/5*4/36
---------
(2/5*4/36)+(3/5*1/36)
Title: Re: S1 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on May 26, 2011, 01:40:26 am
thank you so much dumb economist!
+rep
Title: Re: S1 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on May 26, 2011, 01:47:13 am
Ok...i'll post all my doubts here...pls help me;
1. may/june 2010 p61- qns 2 part2   p62-qns 5 part3and4 qns 7 part4and5      p63-qns6 part 2,3 and4
2.oct/nov 2010 -p63 qns 6 part3 and qns7 part2
3. oct/nov 2009 p61-qns 5(a) part1 and 2 (b) part2 and qns 6 part3
4.may/june 2007 qns 3(b) and 7 part3
5. oct/nov -qns 6 part3 and 7 part3
PLEASE HELP!!!
Title: Re: S1 DOUBTS HERE!!!!
Post by: melony on May 26, 2011, 02:15:15 pm
Quote
thank you so much dumb economist!
+rep

I actually thought u wer dissing him until i read his name lol
Title: Re: S1 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on May 26, 2011, 06:40:55 pm
lol
Title: Re: S1 DOUBTS HERE!!!!
Post by: Aadeez || Zafar on May 26, 2011, 06:42:18 pm
hez was the paper tady(cie
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on May 27, 2011, 04:32:02 am
it was a big upset for me  :'(
Title: Re: S1 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on June 02, 2011, 11:43:25 pm
guys is S1 easier or M1 ???
Title: Re: S1 DOUBTS HERE!!!!
Post by: dj_dead on June 03, 2011, 05:05:40 am
guys is S1 easier or M1 ???



S! anyday !! definitely WAY better dan m1..i mean I actualy ENJOY doin S1..... :O
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on June 04, 2011, 10:42:07 am
guys is S1 easier or M1 ???
if you do physics then M1 is Easy
if you do Commerce then S1 is easier
decide yourselves what do you do or what fell's easy
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on June 04, 2011, 12:30:22 pm
guys is S1 easier or M1 ???

I did both this year!

M1 is good when you understand the concept and practice as much as possible, it's just the calculation part of Physics, so if you take Physics, even with just IGCSE knowledge, that would be fine for you.

S1 is easy to gain marks, and much easier to lose marks due to veryyyy silly mistakes that you may overlook when reading the question, noting down numbers and rounding them off to the correct number of significant figures, yet it's comparatively easier than M1, most of the formulas that you'll use are in the formula booklet and there isn't much of thinking that you'd need to do compared to M1, where you need common sense! :P
Title: Re: S1 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on June 05, 2011, 11:33:37 am
if you do physics then M1 is Easy
if you do Commerce then S1 is easier
decide yourselves what do you do or what fell's easy
well i  ve done igcse phy. only and in commerce ve doev acc and business  ;D
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on June 05, 2011, 11:35:08 am
well i  ve done igcse phy. only and in commerce ve doev acc and business  ;D
then think by yourselves
Title: Re: S1 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on June 05, 2011, 11:37:46 am
I did both this year!

M1 is good when you understand the concept and practice as much as possible, it's just the calculation part of Physics, so if you take Physics, even with just IGCSE knowledge, that would be fine for you.

S1 is easy to gain marks, and much easier to lose marks due to veryyyy silly mistakes that you may overlook when reading the question, noting down numbers and rounding them off to the correct number of significant figures, yet it's comparatively easier than M1, most of the formulas that you'll use are in the formula booklet and there isn't much of thinking that you'd need to do compared to M1, where you need common sense! :P

well basicly actually i 've done phy this year but igcse unfortiunately i cannot express foru how shocked i'm  >:(with what i've done
so when i wanted to decide which paper to take i was like  ::) as all of my friends tookM1 and i was like 'no one to move with me along this route ' :D anyway Thanks for ur advice  ;)
Title: Re: S1 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on June 05, 2011, 12:26:53 pm
then think by yourselves
ofcourse i will do   ;D
 i just wanted to know abt the whole issue as to be able to decide  Thanks
Title: Re: S1 DOUBTS HERE!!!!
Post by: EMO123 on June 05, 2011, 05:56:57 pm
ofcourse i will do   ;D
 i just wanted to know abt the whole issue as to be able to decide  Thanks
hope this all helps
and my wishes that you take  right step ahead
Title: Re: S1 DOUBTS HERE!!!!
Post by: **RoRo** on June 05, 2011, 11:06:41 pm
well basicly actually i 've done phy this year but igcse unfortiunately i cannot express foru how shocked i'm  >:(with what i've done
so when i wanted to decide which paper to take i was like  ::) as all of my friends tookM1 and i was like 'no one to move with me along this route ' :D anyway Thanks for ur advice  ;)

If you didn't like Physics IGCSE, then I'd advice you to go for S1.
The concepts you'd need from IGCSE for M1 are: speed, acceleration, distance, velocity, displacement, force, mass, weight, moments - go through the syllabus if you want, that's speaking of Edexcel's M1 of course.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: perish007 on August 19, 2011, 11:42:38 am
this question is of statistics S1

Find the total number of different 6-digits numbers that can be formed by using the digits 3, 4, 4, 5, 5, 6, 7 .
if one of the number is picked at random, find the probability that
(a) the number is odd,
(b) the number has two digits 5.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Tohru Kyo Sohma on August 19, 2011, 12:15:54 pm
this question is of statistics S1

Find the total number of different 6-digits numbers that can be formed by using the digits 3, 4, 4, 5, 5, 6, 7 .
if one of the digits is picked at random, find the probability that
(a) the number is odd,
(b) the number has two digits 5.
im not sure but is it like this
(a)6!/3!
(b)i didnt get the qns
i dont remember much but if u have the answer u can check with it
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on August 24, 2011, 11:43:14 pm
Find the total number of different 6-digits numbers that can be formed by using the digits 3, 4, 4, 5, 5, 6, 7 .
if one of the number is picked at random, find the probability that
(a) the number is odd,
(b) the number has two digits 5.

Must have 2 4's, or 2 5's or both.
If 2 4's there are 6!/2! different numbers and same for two 5's.
If 2 4's and two 5's then there are 7!/2!2! ways for each choice of the other two numbers. There are three ways the other two can be chosen so altogether 2*6!/2! +3*6!/2! ways altogether.

a) if the number is odd then the last digit is 3, 5 or 7.
If the last digit is 3, then the other 5 numbers can be chosen from 4,4,5,5,6,7
Following the logic above there are 2*5!/2! +2*5!/2! ways of choosing these five. The same result is is 7 is the last number.
If 5 is the last number, and the other 5 numbers contain one 4, there are 5! ways and 5!/2! ways if two 4's.
Hence preb of being odd is (2(2*5!/2! +2*5!/2!)+5!+5!/2!)/2*6!/2! +3*6!/2!)
b)Two 5's so one 4. There are 6!/2! ways this can be down. Prob = 6!/2!/(Find the total number of different 6-digits numbers that can be formed by using the digits 3, 4, 4, 5, 5, 6, 7 .
if one of the number is picked at random, find the probability that
(a) the number is odd,
(b) the number has two digits 5.

Must have 2 4's, or 2 5's or both.
If 2 4's there are 6!/2! different numbers and same for two 5's.
If 2 4's and two 5's then there are 6!/2!2! ways for each choice of the other two numbers. There are three ways the other two can be chosen so altogether 2*6!/2! +3*6!/2! ways altogether.

a) if the number is odd then the last digit is 3, 5 or 7.
If the last digit is 3, then the other 5 numbers can be chosen from 4,4,5,5,6,7
Following the logic above there are 2*5!/2! +2*5!/2! ways of choosing these five. The same result is is 7 is the last number.
If 5 is the last number, and the other 5 numbers contain one 4, there are 5! ways and 5!/2! ways if two 4's.
Hence preb of being odd is (2(2*5!/2! +2*5!/2!)+5!+5!/2!)/2*6!/2! +3*6!/2!)
b)Two 5's so one 4. There are 6!/2! ways this can be done so 6!/2!/(2*6!/2! +3*6!/2!)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 07, 2011, 09:06:06 am
Eight People sit in a minibus: four on the sunny side and four on the shady side. If two people want to sit on opposite sides to each other and another two people want to sit on the shady sides, in how many ways can this be done?
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 07, 2011, 09:25:11 am
here
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 07, 2011, 09:43:47 am
Thanks for clarifying this.. but you have written 6! instead of 4!
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 07, 2011, 09:47:48 am
you are right. Should be 4!
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 07, 2011, 11:24:30 am
Disco Lights are arranged in a vertical line. How many different arrangements can be made from two green, three blue and four red lights if at least eight lights are used?
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 07, 2011, 11:32:33 am
eight lights used
1 red three blue four red 1!*3!*4!
2 red two blue four red 2!*2!*4!
2 red three blue three red 2!*3!*3!
nine lights used 2!*3!*4!
add all these up
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 07, 2011, 04:02:17 pm
Three letters are selected at random from the word SCHOOL. Find the probability that the selection
i. does not contain the letter O,
ii. contains both the letters O.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: iluvme on October 07, 2011, 04:09:42 pm
i. Is it 4/6?

Doing probability maybe after 2 years. :)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 07, 2011, 04:46:10 pm
For both problems, answers are given as 1/5  i took out 2/7 for both.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: iluvme on October 07, 2011, 04:56:42 pm
For both problems, answers are given as 1/5  i took out 2/7 for both.

Sorry maybe someone else would answer.

But why 2/7?
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 07, 2011, 07:21:08 pm
No. of selections with no O's=4c3=4
No. of selections with one O= 4C2=6
No. of selections with two O's=4C1=4
Total Selections=6+4+4=14
P(Does not contain letter O)=4/14=2/7
P(Contains both the letters O)=4/14=2/7
This is how i did but the answers given were 1/5. I think my solution is right but want to confirm it.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on October 11, 2011, 11:20:46 pm
attached Q4 part (b0
and Q5 plz  ??? :'( :'(
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 12, 2011, 08:59:15 am
Try this
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on October 12, 2011, 02:26:16 pm
Try this

Thank you Sir .......... but I'm sorry if I disturbed you by asking you plz could you explain the book answer
attached .................what I don't understand is how he get the probability of sticking to the door choosen before and getting the correct door  ??? ???  :-\ :-\ :-\ :-\
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 12, 2011, 02:37:27 pm
There are three doors and initially the probability of picking the correct door is 1/3
After the host picks one of the two not chosen, it is as if the probability of the car being behind the door he has chosen is given to the one remaining unchosen door. so 1/3 +1/3=2/3
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 14, 2011, 08:21:02 am
Ann, Barry and Clare are three students taking a multiple choice examination paper. For each question a student has to select the correct answer from five that are offered. For Question 1, Ann has no idea of the correct answer, Barry correctly identifies one answer that is wrong and Clare correctly identifies two wrong answers. All three students decide to guess at random from the answers they think stand a chance of being correct. Calculate the probability that:
a. none of the three students chooses the correct answer.
b. Clare is the only one to choose the correct answer.
c. exactly one of the three students chooses the correct answer.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 14, 2011, 09:13:50 am
here
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 18, 2011, 01:50:49 pm
I have one confusion. For the question attached below, if we are said to draw a cumulative frequency curve, then can we use 100,150,200 on the x-axis of the curve or should we use 100.5,150.5,200.5 as we use the value of Upper Class Boundary while drawing C.F curve. I am really confused.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Alpha on October 18, 2011, 01:57:25 pm
I have one confusion. For the question attached below, if we are said to draw a cumulative frequency curve, then can we use 100,150,200 on the x-axis of the curve or should we use 100.5,150.5,200.5 as we use the value of Upper Class Boundary while drawing C.F curve. I am really confused.

You may use 100, 150, 200 etc. You'd use 100.5, 150.5, 200.5 when there wouldn't be an equal sign there.  :)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 18, 2011, 02:09:19 pm
Cant see attachement but use 150 etc anyway
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 18, 2011, 02:23:12 pm
@ astarmathsandphysics you can enlarge the attachment by clicking it. I am still in little confusion. I quote one sentence from my statistics books: "The cumulative frequencies are plotted against the upper class boundaries of the corresponding class." Our class boundary is written in the form x-y where x is inclusive but y is not. However, in the given question 150 200 are inclusive. So, to make it exclusive I add 0.5 and make it 150.5. For this same question mean has also been asked for 4 marks. and it has been done by using 0.5-100.5,100.5-150.5... in the mark scheme.By the way, the full question is from CIE 9709 May June 2011 Paper 61 question no. 6. I also read examiner report. In examiner report the statement was like this: "A mark was awarded for attempting to plot the cumulative frequencies against their respective upper class boundaries"
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Alpha on October 18, 2011, 03:12:35 pm
@ astarmathsandphysics you can enlarge the attachment by clicking it. I am still in little confusion. I quote one sentence from my statistics books: "The cumulative frequencies are plotted against the upper class boundaries of the corresponding class." Our class boundary is written in the form x-y where x is inclusive but y is not. However, in the given question 150 200 are inclusive. So, to make it exclusive I add 0.5 and make it 150.5. For this same question mean has also been asked for 4 marks. and it has been done by using 0.5-100.5,100.5-150.5... in the mark scheme.By the way, the full question is from CIE 9709 May June 2011 Paper 61 question no. 6. I also read examiner report. In examiner report the statement was like this: "A mark was awarded for attempting to plot the cumulative frequencies against their respective upper class boundaries"

I did that paper some time back. And I got the same confusion as yours.

Yeah, now I get what you mean. You're right. Less or equal to 100 means it stops at 100. So, you cannot use 100 as the starting point for the other class. You have to add 0.5. Make it 100.5.
It's actually the difference between a discrete and continuous variable. The cumulative frequency uses a continuous variable, when you convert it to a simple frequency table, it becomes a discrete variable.

Hope you get me. :)

And thanks for asking that question. My confusion is cleared, albeit by myself.:P
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: lastgift on October 19, 2011, 10:58:17 pm
Hi! Doubt in a continuous random variable question.
Q) 5 from this paper attached!
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 19, 2011, 11:45:47 pm
here
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 22, 2011, 01:22:23 pm
1.
A machine is used to fill cans of soup with a nominal volume of 0.450 litres. Suppose that the machine delivers a quantity of Soup which is normally fistributed with mean x litres and standard deviation y litres. Given that x= 0.457 and y= 0.004, find the probability thata randomly chosen can will contain less than the nominal value.[Ans:0.0401]
It is required by law that no more than 1% of cans contain less than the nominal volume
Find.
i. the least value of x which will comply with the law if y=0.004 [Ans:0.459]
ii. the greatest value of y which will comply wit the law if x= 0.457 [Ans:0.003]
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 22, 2011, 02:17:01 pm
Give me time to get to pc
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ashwinkandel on October 22, 2011, 05:27:01 pm
One more confusion:

Q. On a particular day, 50% of the employees in a large company had arrived at work by 8.30 am, and 10% had not arrived by 8.55 am.
a. Assuming a normal modal, find the standard deviation of arrival times, in minutes.[Ans:19.50]
b. It is given that only 5% of the employees had arrived by 8.05 am. Without further calculation, explain why this might suggest that normal model is not appropriate [Ans: not symmetrical ... but can you give me explanation..... what is means..]
c. Eighty employees are selected at random. Find the expectation of the number of these employees that arrived between 8.30 and 8.55 a.m.[Ans:32] 
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 23, 2011, 09:59:49 am
1st questions above
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on October 23, 2011, 10:00:46 am
last question above
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on November 20, 2011, 11:46:44 am
I am taking CIE statistics 1 this year.
I have doubts relating to mean,median and mode. Although they are just the basics, i am still confused:

1) whenever we draw a histogram, do we always have to take 'frequency densities' on the y-axis? Or do we also take 'frequency' on the y-axis?

2) for grouped data, and the frequencies given, how do we find the median without drawing the cummulative frequency graph?

3) for grouped data, and frequencies given, how do we find the upper quartile and lower quartile?

4) what is the difference between variance and standard deviation?

Thanks.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on November 20, 2011, 04:07:40 pm
anyone who can answer my questions? Pls.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 20, 2011, 10:51:44 pm
You have to use frequency densities if the class intervals are not the same. Personally I think it is always better to use them cos you get used to them.
Variance = standard deviation squared.
For the median and quartile stuff see
http://www.astarmathsandphysics.com/a_level_maths_notes/S1/a_level_maths_notes_s1_quartiles_and_median_from_frequency_tables.html
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on November 21, 2011, 12:37:21 pm
^^thankyou.  now i can understand better and continue with my practice. :)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 21, 2011, 02:21:15 pm
no probs
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on November 24, 2011, 09:51:54 am
here's a question

Q) the mean snd standard deviation of the heights of 12 boys in a class are 148.8 and 5.4 cm respectively. A boy of height 153.4 cm joins the class. Find the mean and standard deviatiation of the 13 boys.

I found the mean but cant find SD.
____________________________

theres are formulas for finding median and quartiles in grouped data. But what if the data is not grouped and has large frequences and is summarised in a table.then how do we find the quartiles?
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 24, 2011, 10:37:29 am

see attachment
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on November 24, 2011, 11:12:12 am
here is my question plz explain his answer
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 24, 2011, 11:28:52 am
reasonable for the values given in the table as someone could easily practice 20 hours a week and professional musicians pactrice up to 60 or more. Not reasonable for 168 as only 168 hours in week.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on November 24, 2011, 12:09:26 pm
reasonable for the values given in the table as someone could easily practice 20 hours a week and professional musicians pactrice up to 60 or more. Not reasonable for 168 as only 168 hours in week.

Sir , I'm sorry but from where did you get these values ...is there anymore clarification ???
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 24, 2011, 12:22:03 pm
Number of hourse x between 1 and 15 and number of hours y between 4 and 18 in the table in your attachment
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on November 24, 2011, 01:38:25 pm
reasonable for the values given in the table as someone could easily practice 20 hours a week and professional musicians pactrice up to 60 or more. Not reasonable for 168 as only 168 hours in week.

which  means that the graph will curve as it cease to be proportionalor form a linear relationship..........right ???  ::) ::) ::)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 24, 2011, 02:21:38 pm
Yes and it will definitetely curve as nutters practice 168 hours a week and make less than zero mistakes
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on November 24, 2011, 02:24:54 pm
Yes and it will definitetely curve as nutters practice 168 hours a week and make less than zero mistakes

yes Thanks alot Sir  ;D
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on November 25, 2011, 05:38:37 pm
thankyou sir, i got how to do it.
But could you pls answer my other question?
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 25, 2011, 07:59:17 pm
Is that the quantiles question?
http://www.astarmathsandphysics.com/a_level_maths_notes/S1/a_level_maths_notes_s1_quartiles_and_median_from_frequency_tables.html
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on November 26, 2011, 12:11:14 pm
no sir. I am sorry but this isnt exactly my doubt. I wanted to know how we find the quartiles for large data with no classes.
For example:

Score          :     0       1         2       3       4      5      6
frequency :   36      94     48     15     7      3      1
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 26, 2011, 10:21:15 pm
For this one, there are 36+94+48+15+7+3+1=214
I would do this:214/4=53.5 so the lower quartile is 1
For the upper quartile find 3/4*215=160.5 so the upper quartile is 2
More complicated methods exist but for S1 do as above..
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on November 27, 2011, 03:25:40 pm
thankyou,sir.oh, but my i already know about this method, but when solving some questions like this, i sometimes get the wrong answer.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on November 27, 2011, 11:23:32 pm
Give examples. This method is for Edexcel.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on December 01, 2011, 12:16:44 pm
A question:
An ordinary dice was thrown 50 times and the resulting scores were summarised in a frequency table. The mean score was calculated to be 3.42. It was later found that the frequencies 12 and 9,of two consecutive scores,had been swapped. What is the correct value of the mean?
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 01, 2011, 12:28:51 pm
differene of12n+9(n-1)-12(n-1)-9n==12-9=3
3/50=0.06
3.42+0.06=3.48
or 3.42-0.06=3.36
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Sea Lover on December 07, 2011, 03:22:20 pm
can somone help me with these two questions:
1-Three letters are selected at random from the word SCHOOL.Find the probablity that the selection:
a)does not contain the letter O
b)contains both letters O

2-In how many different ways can a football team of 11 players be photographed if there are to be two rows ,with 5 seated on the front row and 6 standing in the back row?In how many of these photographswould the captain be sitting in the centre of the front row?
thanx in adavnce
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 07, 2011, 05:52:12 pm
1a.4/6*3/5=12/30=2/5
b.2/6*1/5=1/15

2.11! cos each player is an individual and they can be told apart.
The captain can sit on the front in one of five places and the others can arrange themselves in 10! ways so5*10!
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 08, 2011, 10:43:52 am
1a.4/6*3/5=12/30=2/5
b.2/6*1/5=1/15

2.11! cos each player is an individual and they can be told apart.
The captain can sit on the front in one of five places and the others can arrange themselves in 10! ways so5*10!

Sir why how did you find the first answer ??? why did you mulitply 4/6 * 3/5 ...???
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 08, 2011, 10:57:01 am
cos there are four non 'o' letters out of 6 so prob of not picking o is 4/6
when this letter is picked, there are three non 'o' letters out of five, so prob of picking non 'o' letter is 3/5
then 4/6*3/5
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 08, 2011, 10:58:21 am
theeducationchannel.info is working now. You can also ask for a 'video solution'
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 08, 2011, 11:37:19 am
cos there are four non 'o' letters out of 6 so prob of not picking o is 4/6
when this letter is picked, there are three non 'o' letters out of five, so prob of picking non 'o' letter is 3/5
then 4/6*3/5

but that's with assuming that the number is not replaced ......right ??? ok if that's the case then it might me 4/6*3/5*2/4 as he picked three numbers right ???

Thanks for the link I'll try it  ;)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 08, 2011, 11:51:47 am
exactly
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 08, 2011, 11:52:12 am
That's me in the videos
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 15, 2011, 09:34:36 am
hello

I would really appreciate it if someone explain the atttached question for me

Thanks in advance  :)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 15, 2011, 02:42:07 pm
z=(23-25)/4=-.5
look this up. Since -.05<0, look up 0.5 and subtract from 1.
1-0.6915=0.3085
Since this is for each of the three bikes the answer is 0.3085^3
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 15, 2011, 02:59:56 pm
z=(23-25)/4=-.5
look this up. Since -.05<0, look up 0.5 and subtract from 1.
1-0.6915=0.3085
Since this is for each of the three bikes the answer is 0.3085^3

Sir I did the same but the answer was that one
attached
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 16, 2011, 08:53:23 am
They are wrong. Phone them and tell them.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 16, 2011, 09:32:32 am
They are wrong. Phone them and tell them.

Actually if I do have their number I would do  immediately  ;)


here is other question which I want to be sure about it

why the Q3 is not 34 only
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 16, 2011, 10:09:24 am
They have done it the way I would do it.
Note that if you have 3 number 1,5,7 the middle is the second, the middle of the first and third one (1+3)/2=2
There are 30 numbers so 3/4(1+30)=23.25
34 is the 23rd one but I want the 23.25th one so go 1/4 of the way from 34 to 36 which is 1/2 then add it to 34.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 16, 2011, 04:50:25 pm
They have done it the way I would do it.
Note that if you have 3 number 1,5,7 the middle is the second, the middle of the first and third one (1+3)/2=2
There are 30 numbers so 3/4(1+30)=23.25
34 is the 23rd one but I want the 23.25th one so go 1/4 of the way from 34 to 36 which is 1/2 then add it to 34.

then how the Q1 was 19 ???

Sir is that method above known ??? I mean in my S1 book they never taught us about this method just find 75% of the no. then if it is not a whole no. then round up and find the corresponding term


 :-X
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 17, 2011, 09:29:30 am
I know. I don't like the book method - it is technically incorrect. My method is the statistically correct method.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 17, 2011, 02:51:44 pm
I know. I don't like the book method - it is technically incorrect. My method is the statistically correct method.

ok can plz Sir give me the equations for :
Q1
Q2
Q3 by your method
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 17, 2011, 05:53:31 pm
There is no equation but actually a method. I treat a list as continuous and use
1/4 (n+1) for lower quartile
1/2 (n+1) for median
3/4 (n+1) for upper quartile.
If any of these result in a decimal I interpolate as I did for your question.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 17, 2011, 06:27:56 pm
There is no equation but actually a method. I treat a list as continuous and use
1/4 (n+1) for lower quartile
1/2 (n+1) for median
3/4 (n+1) for upper quartile.
If any of these result in a decimal I interpolate as I did for your question.

Thanks alot Sir
 Q1 -the above method can be used for Edexcel too ???
Q2 in the attached pic. it's wrong I'm pretty sure but want to know if you agree  or not ???

Thanks in advance  :D
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 19, 2011, 11:54:35 am
negative skew actually since longer tale on left than right.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 19, 2011, 12:32:01 pm
negative skew actually since longer tale on left than right.


hahaha.....Thanks alot
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 25, 2011, 01:29:36 pm
Sir plz explain that question  :o
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 25, 2011, 03:33:48 pm
because you can have two vowels in three different ways
VVC
VCV
CVV
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 25, 2011, 04:39:10 pm
because you can have two vowels in three different ways
VVC
VCV
CVV

ohhhhhhh.....it's that simple ??? ......

Thanks alot Sir  ;)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on December 26, 2011, 07:46:39 pm
No probs
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on December 28, 2011, 01:52:40 pm
Sir , I don't understand in (f) in the attached question
Could you please explain it by your own way as the mark scheme is confusing enough for me  ??? ???

ADDED DOUBT

part (c) the 2nd line plz in answer
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 04, 2012, 08:54:26 am
Positive skew. The skew is always in the direction of the tail, where there are less readings.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on January 05, 2012, 06:42:17 am
Positive skew. The skew is always in the direction of the tail, where there are less readings.

ahaaaa...so I can't get it from the box plot but what I shloud think about is the attached one right
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on January 05, 2012, 08:15:17 am
2 question to answer plz  ???

regarding the first question what I don't understand is why he didn't use ''square root 10'' as a standard variation ??? what's your opinion
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 05, 2012, 09:44:16 pm
Your skew diagram is exactly right
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 05, 2012, 09:47:33 pm
Normal distribution is written N(mean, standard deviation^2) so standard deviation = sigma=10
As for the second I will post an attachment
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 05, 2012, 09:57:28 pm
here
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on January 06, 2012, 06:52:16 am
here

Thanks alot Sir
+rep

also plz see my answer to this one which one is right ???
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 06, 2012, 11:54:43 pm
You are using sqrt(10) as the standard deviation but it is 10.
They have the correct zanswer
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on January 07, 2012, 06:58:02 am
You are using sqrt(10) as the standard deviation but it is 10.
They have the correct zanswer

Sir Thanks ...........can you plz  look here

I'm sorry........
I know I might be asking too  much about that question but I really want to understand it  :-[ :-[ :-[ :-[ :-[ :-[
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 07, 2012, 11:12:42 pm
It says sigma^2=10^2
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on January 14, 2012, 10:28:25 pm
here we go exam after tom...hoping for a good..soon reply  :-[  :-\
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Aayesha on January 15, 2012, 05:01:34 am
has any one done s1 edexcel june 2011 q8 (g) and June 2004 S1 edexcel q5 (C)?
Please help!
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Deadly_king on January 15, 2012, 05:10:01 am
has any one done s1 edexcel june 2011 q8 (g) and June 2004 S1 edexcel q5 (C)?
Please help!

I think it would be best of you provided a link to the paper or posted the whole question since many of us do not have the paper at hand :(
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Aayesha on January 15, 2012, 05:38:34 am
http://www.xtremepapers.com/Edexcel/Advanced%20Level/Mathematics/2004%20June/S1Jun04Q.pdf
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Aayesha on January 15, 2012, 05:39:44 am
june 2011.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 15, 2012, 05:59:14 am
Miss relina will do your q when I get home
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 16, 2012, 09:01:59 am
Just 4 u miss relina
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: ~ Miss Relina ~ on January 16, 2012, 04:54:01 pm
Just 4 u miss relina

OMG!!!!!!!!!!!  :o :o :o :o...I don't know how can I thank you  :-[ :-[

I can not find the words to say that you are MY LIFE SAVER..........PERFECT   8)

I 've posted these questions on TSR but people there are kind of lazy ::) and annoying  :-\

but you really helped me throughout my long journey ..alllll credit goes to you  ;D  :-*

Thanks alot Sir   ;) ;) ;) ;) :) :) :)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on January 17, 2012, 07:59:07 pm
No probs. Pass the goodwill around
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on February 19, 2012, 11:47:05 am
Q) I have 7 fruit bars to last a week. 2 are apricot, 3 are fig and 2 are peach. I select one bar each day. In how many different orders can i eat the bars?
If i select a fruit bar at random each day,what is the probability that i eat the 2 apricot ones on consecutive days?
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 19, 2012, 12:17:48 pm
7/(2!3!2!)
6/(7/(2!3!2!))
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on February 19, 2012, 03:10:54 pm
7/(2!3!2!)
6/(7/(2!3!2!))
thankyou for answering the question but the book answers given in the book are, 210 and 2/7.

And i got a couple of more doubts:

Q) 6 people are going to travel in a six-seater minibus but only 3 of them can drive. In how many diffrent ways can they seat themselves?

Q) 10 people travel in 2 cars, a saloon and a mini. If the saloon has seats for six and the mini has seats for 4, find the number of different ways the party can travel, assuming that the order of seating in each car does not matter and all the people can drive.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 20, 2012, 02:45:38 pm
should be 7!/(2!3!2!) and 6/(7!(2!3!2!))
1. first pick the driver - choice of three and the remaining 5 can sit in 5! ways so 3*5!
2.10!/(4!6!)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on February 20, 2012, 03:10:03 pm
thankyou sir, got it.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 20, 2012, 11:48:25 pm
good go see the tests here on my website.
Putting up two good tests every day now
http://www.astarmathsandphysics.com/test_centre/
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on February 23, 2012, 08:31:16 pm
good go see the tests here on my website.
Putting up two good tests every day now
http://www.astarmathsandphysics.com/test_centre/
found just what i was looking for. The tests are perfect for my revision. Thankyou sir.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 24, 2012, 09:31:31 am
Thanks. Any tests in particular you need ask me.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on February 27, 2012, 11:57:19 am
Thanks. Any tests in particular you need ask me.
well, i find permutations and combinations questions a little confusing so thats what i need the most practise for.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 27, 2012, 12:25:42 pm
I have done 3 tests and will put them uptonight
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: silvercameron on February 28, 2012, 07:59:20 pm
I have done 3 tests and will put them uptonight
nice tests. Thankyou sir.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on February 28, 2012, 09:06:42 pm
they are up now. try them. more on way
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: LekhB on March 01, 2012, 07:08:51 am
Hi

I can't figure out how to answer this question:

On a particular farm, 60% of all eggs laid by hens are classified 'large'. Everyday, the farmer selects the same number of eggs at random and sends them as a batch to the market. Given that the standard deviation of the number of eggs in a batch is 12, find
(a) the number of eggs in a batch,
(b) the mean number of large eggs in a batch.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on March 01, 2012, 09:00:31 am
12=sqrt(np(1-p))
144=n*0.6*0.4 so n=600
Mean=np=600*0.6=360
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: LekhB on March 01, 2012, 10:49:52 am
I don't believe it was that easy. Thanks!
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on March 01, 2012, 11:09:41 am
See my S1 videos here
http://theeducationchannel.info/videos/18/A-Level-Maths-S1/most_recent/all_time/
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: LekhB on March 01, 2012, 01:05:34 pm
A commuter, who caught the same rain to work everyday, kept a recod over six months and found that the train was late on 49 days out of a total of 126 working days. Use a binomial probability model to estimate the probability that, in five day working week, the train will be late exactly 3 times. State briefly, giving reasons, whether a binomial model is likely to be a satisfactory or unsatisfactory mathematical model in this situation.
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on March 01, 2012, 01:52:01 pm
p=49/126=7/18
P(Late 3 times)=5C3*(7/18)^3*(11/18)^2=0.2196
not suitable cos of strikes etc (in UK at least)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: SauD~ on March 03, 2012, 12:14:57 pm
Can anyone explain me about permutation? With few examples?
Thanks,
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: astarmathsandphysics on March 03, 2012, 04:24:06 pm
I can explain 2000 times today
See the first two videos here
http://theeducationchannel.info/videos/18/A-Level-Maths-S1/most_recent/all_time/
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: polltery on May 12, 2012, 08:06:20 am
A box contains 300 discs of different colours. There are 100 pink discs, 100 blue discs and 100 orange
discs. The discs of each colour are numbered from 0 to 99. Five discs are selected at random, one at
a time, with replacement. Find

(ii) the probability that exactly 2 discs with numbers ending in a 6 are selected, [3]

The marking Scheme says:
P(2 end in 6) = (1/10)2 × (9/10)3 × 5C2 =0.0729

My doubt is..
How on earth is prob success is 1/10???!
for a single disc to be numbered 6.. i am getting 1/100
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 12, 2012, 08:17:48 am
Read the question properly brother. It doesn't say "Numbered 6", it says "ending in a 6".

6, 16, 26, 36, 46, 56, 66, 76, 87, 96. 10 numbers from 100. 10/100 = 1/10

I think you can figure out the rest :)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: polltery on May 12, 2012, 08:27:40 am
whoooaaa! jeez, thanks alot bro! :D
that paper trolled the hell outta me xD
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Ghost Of Highbury on May 12, 2012, 09:04:38 am
:)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: red_911 on May 12, 2012, 03:01:20 pm
HI,
Can anyone please tell me hoe to do S1 january 2012 question 7 part C .. tried alot but cant understand ???
thanks :)
Title: Re: S1 and S2 DOUBTS HERE!!!!
Post by: Alpha on May 25, 2012, 09:39:22 am
HI,
Can anyone please tell me hoe to do S1 january 2012 question 7 part C .. tried alot but cant understand ???
thanks :)

Link to the paper?