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Probability - Columbus elementary school

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by Brent@GMATPrepNow » Sun Dec 28, 2008 11:10 am
If a child is randomly selected from Columbus elementary school, what is the probability that the child will be a boy?

(1) If 25 boys are removed from the school, the probability of selecting a boy will be 0.75
(2) There are 35 more boys than girls
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by cramya » Sun Dec 28, 2008 11:15 am
Hope I dint fall in to the trap.

Is it C)?

x->boys
y->girls

Stmt I

x+75 = 3y

Stmt II

y = x-35

Together solve for x and y

(If I did fall in to the trap then its between A and C)
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by Brent@GMATPrepNow » Sun Dec 28, 2008 12:42 pm
The answer is, indeed, C.
Nice work, cramya!
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by cramya » Sun Dec 28, 2008 12:47 pm
Thanks to you for coming back after the christmas break and posting some good questions!

Wish u a happy new year!
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by vittalgmat » Sun Dec 28, 2008 8:20 pm
Hi Cramya,
I am getting a different eqn in stmt 1.
here is my approach. let me know if something is wrong.

(B - 25) / (B -25 +G) = 3/4

-> 4B - 100 = 3B -75 +3G
-> 4B-3B = 100-75 +3G
-> B = 25 +3G
-> B -25 = 3G

However, this does not affect the final result.
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by cramya » Sun Dec 28, 2008 8:23 pm
Vittal, Urs is correct. There should be a -25 in the numerator
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