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What is the probability for a family with three children to

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Senior Manager
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What is the probability for a family with three children to [#permalink] New post 17 Apr 2006, 05:45
26. What is the probability for a family with three children to have a boy and two girls (assuming the probability of having a boy or a girl is equal)?

a) 1/8
b) ¼
c) ½
d) 3/8
e) 5/8
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 [#permalink] New post 17 Apr 2006, 06:29
My solution:

BGG : 1/2 * 1/2 * 1/2 = 1/8
GBG: 1/8
GGB: 1/8

So the probability is 3/8 which is the same as BG

BG can U explain your solution, I dont think I get it
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 [#permalink] New post 17 Apr 2006, 06:43
This is the binominal formula, which gives all possible outcomes.
prob 3b=1/8
prob 2b1g=3/8
prob2g1b=3/8
prob 3g=1/8
when you sum up this you get 1
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 [#permalink] New post 17 Apr 2006, 07:40
I think it is B, 1/4.

A family with 3 children can have either

BBB
BBG
BGG
GGG


Only one out of four is the required combination.

- Vipin
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 [#permalink] New post 17 Apr 2006, 08:04
vipin7um wrote:
I think it is B, 1/4.

A family with 3 children can have either

BBB
BBG
BGG
GGG


Only one out of four is the required combination.

- Vipin


No this wouldn't be. The correct answer is 3/8.

Thanks,
Vipin
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Re: P&C - 3 [#permalink] New post 17 Apr 2006, 17:55
gmatacer wrote:
26. What is the probability for a family with three children to have a boy and two girls (assuming the probability of having a boy or a girl is equal)?

a) 1/8
b) ¼
c) ½
d) 3/8
e) 5/8


X= # of girls

P(X=2) when n=3

P(x=2) = 3c2 * (1/2)^2 * 1/2

= 3/8
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 [#permalink] New post 17 Apr 2006, 22:18
I have trouble finding the p in the binominal formula. How did you find p to be 1/2?
  [#permalink] 17 Apr 2006, 22:18
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