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Dec. 3rd, 2008 10:05 amQ: A couple has two children, one of whom is a girl. What is the probability that the other one is a girl?

A: 1/3

Answers from other people:

**trollprincess**-- 50/50

**louiselux**-- a 50/50 chance?

**crossbow1**-- 50/50

**omylouse**-- 0.5

**debauchingbeast**-- half?

**slicesmissus**-- 1 in 2?

**eor**-- Approximately 1 in 2.

**enigma_o**-- 50% or 0% depending on how you take 'one of whom'

**letting_it_out**-- Fifty-fifty

**mollydot**-- 50%

**invisigoth51**-- 50%

Everyone disagrees with me! And people are still arguing with me in the comments of that post, so I assume I am not explaining myself well. So, some links for you!

Wikipedia: Boy or Girl paradox. (Pf, it is not really a paradox.) The question I asked corresponds to the second question on that page: they ask "A random two-child family with at least one boy is chosen. What is the probability that it has a girl?", so their answer is 1 - my answer.

Ask Dr Math: a forum thread of some people talking about this question (but with two boys instead of two girls).

Cut The Knot has two examples: one where for some reason they have bears instead of children, and one using black and white counters.

I hope these are useful in understanding the problem! :)