> If you don't specify which child is a girl, only that one is, then it's 1/3 You mean, if you only specify that at least one child is a girl, then it's 1/3.

> If you don't specify which child is a girl, only that one is, then it's 1/3 You mean, if you only specify that at least one child is a girl, then it's 1/3. Actually you're still underspecified, because you haven't said what you do if the parent has no girls.