IGCSE MATHS Doubts

[Ghost Of Highbury]

https://studentforums.biz/index.php/topic,7273.msg206902.html#msg206902

[saleemsamer]

O/N 06 p4 q5 b and c with explanation plz

[Choc.Kits]

Hey guys. Im having trouble on a question. Its:

November 2009, Paper 4, Question 7 (c)(i) and (ii)

Thank you!

[Ghost Of Highbury]

Hey guys. Im having trouble on a question. Its:

November 2009, Paper 4, Question 7 (c)(i) and (ii)

Thank you!

Radius = X
Height = y

Volume or W = 1/3 * x^2 * y * pi = (x^2ypi)/3

3 times --> Radius = 3x
Height = 3y

VOlume = 1/3 * pi * (3x)^2 * 3y = 9x^2y*pi

W = (x^2ypi)/3
Vol. =  9x^2y*pi

W * 27 = Vol.

27W
----------

cii) Radius = 2x

      Height = y

Vol. = 1/3 * pi * (2x)^2 * y = (4x^2ypi)/3

W = (x^2ypi)/3

W * 4 = Vol.

Therefore, 4W

PS : Volume of a cone = 1/3*pi*r^2*h

[saleemsamer]

O/N 06 p4 q5 b and c with explanation plz

any1?

[Ghost Of Highbury]

O/N 06 p4 q5 b and c with explanation plz

bi) Hits , Hits and Hits. = 1/3*1/3*1/3 = 1/27

bii) The probability that she never hits is 2/3*2/3*2/3 = 8/27

1 - 8/27 = 19/27

c)i) Hits in 4th throw = Doesnt hit, Doesnt Hit, Doesnt Hit, Hits.

Doesnt hit = 1- 1/4 = 3/4

3/4 * 3/4 * 3/4 * 1/4 = 27/256


cii) This means that he "Doesnt hit" till the nth throw. Till the nth throw means that he doesnt hit for the first (n-1)th throw.

     LIke (ci), u multiply 3/4 for (n-1) times and multiply it with 1/4

Therefore, (3/4)^(n-1) * 1/4

 
                          

                              

[saleemsamer]

bi) Hits , Hits and Hits. = 1/3*1/3*1/3 = 1/27

bii) The probability that she never hits is 2/3*2/3*2/3 = 8/27

1 - 8/27 = 19/27

thx but wat bout c?



 
                          

                              

[Ghost Of Highbury]

bi) Hits , Hits and Hits. = 1/3*1/3*1/3 = 1/27

bii) The probability that she never hits is 2/3*2/3*2/3 = 8/27

1 - 8/27 = 19/27

thx but wat bout c?

check again.

[saleemsamer]

check again.

lol Thank You

[Ghost Of Highbury]

lol Thank You

No problemo

[Choc.Kits]

Radius = X
Height = y

Volume or W = 1/3 * x^2 * y * pi = (x^2ypi)/3

3 times --> Radius = 3x
Height = 3y

VOlume = 1/3 * pi * (3x)^2 * 3y = 9x^2y*pi

W = (x^2ypi)/3
Vol. =  9x^2y*pi

W * 27 = Vol.

27W
----------

cii) Radius = 2x

      Height = y

Vol. = 1/3 * pi * (2x)^2 * y = (4x^2ypi)/3

W = (x^2ypi)/3

W * 4 = Vol.

Therefore, 4W

PS : Volume of a cone = 1/3*pi*r^2*h

Thanks a billion for that reply! I owe you

[Ghost Of Highbury]

Your welcome ..

[Mr.DitD]

Hello everyone!!!

Can some1 please explain this question:

(c) A different cone, with radius x and height y, has a volume W.

Find, in terms of W, the volume of: (ii) a cone of radius 2x and height y.

http://www.freeexampapers.us/IGCSE/Maths/CIE/2009%20Nov/0580_w09_qp_4.pdf  Q7 part (c)

 

[Vin]

[

Hello everyone!!!
Can some1 please explain this question:
(c) A different cone, with radius x and height y, has a volume W.

Radius = X
Height = y

Volume or W = 1/3 * x^2 * y * pi = (x^2ypi)/3

3 times --> Radius = 3x
Height = 3y

VOlume = 1/3 * pi * (3x)^2 * 3y = 9x^2y*pi

W = (x^2ypi)/3
Vol. =  9x^2y*pi

W * 27 = Vol.

27W
----------

cii) Radius = 2x

      Height = y

Vol. = 1/3 * pi * (2x)^2 * y = (4x^2ypi)/3

W = (x^2ypi)/3

W * 4 = Vol.

Therefore, 4W

PS : Volume of a cone = 1/3*pi*r^2*h

[Mr.DitD]

[

I understand that Vol. = 1/3 * pi * (2x)^2 * y

But i dont know how it becomes: (4x^2ypi)/3

Can u please explain furthur if possible? Thanks a lot!!