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Author Topic: S1 and S2 DOUBTS HERE!!!!  (Read 54201 times)

Offline silvercameron

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #345 on: February 23, 2012, 08:31:16 pm »
Quote from: 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/
found just what i was looking for. The tests are perfect for my revision. Thankyou sir.
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Offline astarmathsandphysics

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #346 on: February 24, 2012, 09:31:31 am »
Thanks. Any tests in particular you need ask me.
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Offline silvercameron

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #347 on: February 27, 2012, 11:57:19 am »
Quote from: astarmathsandphysics on February 24, 2012, 09:31:31 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.
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Offline astarmathsandphysics

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #348 on: February 27, 2012, 12:25:42 pm »
I have done 3 tests and will put them uptonight
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Offline silvercameron

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #349 on: February 28, 2012, 07:59:20 pm »
Quote from: astarmathsandphysics on February 27, 2012, 12:25:42 pm
I have done 3 tests and will put them uptonight
nice tests. Thankyou sir.
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Offline astarmathsandphysics

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #350 on: February 28, 2012, 09:06:42 pm »
they are up now. try them. more on way
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Offline LekhB

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #351 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.
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Offline astarmathsandphysics

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #352 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
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Offline LekhB

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #353 on: March 01, 2012, 10:49:52 am »
I don't believe it was that easy. Thanks!
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Offline astarmathsandphysics

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #354 on: March 01, 2012, 11:09:41 am »
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Offline LekhB

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #355 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.
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Offline astarmathsandphysics

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #356 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)
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Offline SauD~

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #357 on: March 03, 2012, 12:14:57 pm »
Can anyone explain me about permutation? With few examples?
Thanks,
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Offline astarmathsandphysics

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #358 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/
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Offline polltery

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Re: S1 and S2 DOUBTS HERE!!!!
« Reply #359 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
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