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A woman has two kids. One is a boy. What are the odds the other is a boy?

Poll: What are the odds?
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100%
1.15%
 1 1.15%
50%
79.31%
 69 79.31%
33%
16.09%
 14 16.09%
25%
3.45%
 3 3.45%
Total 87 vote(s) 100%
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A woman has two kids. One is a boy. What are the odds the other is a boy?
Spaz
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#83
2009-03-12, 11:12 PM
Read the question carefully, guys. It doesn't say "the first kid is a boy", it just says one is. These are the 4 possibilities, with equal probability, without knowing anything other than there are 2 kids:

BB
BG
GB
GG

If the question did say "the first kid is a boy" then it would be:

BB
BG
GB
GG

And it would be 50% chance of the other being a boy. But it doesn't say that, it just says one of the two is a boy. That makes it:

BB
BG
GB
GG

and therefore 33% chance of them both being boys.

Anyone want to make a post about the birthday paradox? Goggleemoticon
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A woman has two kids. One is a boy. What are the odds the other is a boy? - by Spaz - 2009-03-12, 11:12 PM

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