Who knew siblings could be so complicated??

RainGame · 10-9-2005, 10:49 PM

Here's a little riddle that ought to make you think..

If a family has two children and the older child is a boy, there is a 50 percent chance the family will have two boys.

So the four possibilities are: (older, younger)
(b:g) (g:g)
(b:b) (g:b)

We know that the older is a boy, so that only leaves two outcomes, perfectly explaining why there is a 50% chance of having two boys.

But say you didn't know whether the boy was older or younger, that would only eliminate the g:g possibility, leaving three others. So the odds of a b:b are 1/3.

So how can the age of the boy determine the chance of the other child being a boy or a girl?

10-9-2005, 10:49 PM	#1
RainGame FFR Player Join Date: Oct 2005 Posts: 1	Who knew siblings could be so complicated?? Here's a little riddle that ought to make you think.. If a family has two children and the older child is a boy, there is a 50 percent chance the family will have two boys. So the four possibilities are: (older, younger) (b:g) (g:g) (b:b) (g:b) We know that the older is a boy, so that only leaves two outcomes, perfectly explaining why there is a 50% chance of having two boys. But say you didn't know whether the boy was older or younger, that would only eliminate the g:g possibility, leaving three others. So the odds of a b:b are 1/3. So how can the age of the boy determine the chance of the other child being a boy or a girl?

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