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# There is a family with two children. One is a boy, what is

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There is a family with two children. One is a boy, what is [#permalink]

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14 Feb 2004, 23:35
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

There is a family with two children. One is a boy, what is the
probability that the other is a girl?
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14 Feb 2004, 23:54
1/2 if the fact that the first kid being a boy is independent of the second kid being a girl
1/4 if the question is about the probability of having first kid a boy and second kid a girl
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Paul

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15 Feb 2004, 05:30
I stand by Paul on this one.

Hi Paul,

By any chance r u registered at TestMagic as Paul78 ?

Anand.
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15 Feb 2004, 06:10
Paul wrote:
1/2 if the fact that the first kid being a boy is independent of the second kid being a girl
1/4 if the question is about the probability of having first kid a boy and second kid a girl

Sex of any baby is indepedent of its siblings.
Question stem does not say the first baby is boy.
All it says is one is boy.
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15 Feb 2004, 06:40
Then what we have is

BG GB GG BB
so dsired events are BG and GB total events are 4
2/4 = 1/2
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15 Feb 2004, 07:07

But, here is my explanation.

Total possibilities = BB, GG, BG, GB
One(Atleast) is BOY = BB, BG, GB
Another is Girl,given than other is BOY = BG , GB

P = 2/3.

As i said before, I don't have official answer!
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15 Feb 2004, 09:11
interesting reasoning kpadma. Indeed, you would then have to remove GG to get 2/3. I think it should be right then. Anandnk, yes i'm paul78 on testmagic. Put the same signature so that you could recognize me... you stalker!
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17 Feb 2004, 06:29

But, here is my explanation.

Total possibilities = BB, GG, BG, GB
One(Atleast) is BOY = BB, BG, GB
Another is Girl,given than other is BOY = BG , GB

P = 2/3.

As i said before, I don't have official answer!

The question should be worded "at least one is a boy" and in that case, 2/3 is the answer. Trust me.

However, as worded, the question states: "ONE is a boy". hence the other child MUST be a girl. If the other was a boy, then the statement "ONE is a boy" would not be true -- because in that case TWO of them are boys!

Of course, this is an oversight and the GMAT would not be so ambiguous.

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AkamaiBrah
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993

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17 Feb 2004, 07:26
AkamaiBrah wrote:
The question should be worded "at least one is a boy" and in that case, 2/3 is the answer. Trust me.

However, as worded, the question states: "ONE is a boy". hence the other child MUST be a girl. If the other was a boy, then the statement "ONE is a boy" would not be true -- because in that case TWO of them are boys!

Of course, this is an oversight and the GMAT would not be so ambiguous.

Yes, Adding "atleast" makes the question clearer.
Thanks Akamai!
17 Feb 2004, 07:26
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