1. The problem statement, all variables and given/known data I have two kids. Given that at least one of them is a girl, what is the probability that they are both girls? 2. Relevant equations 3. The attempt at a solution I think it's 1/3, because the possibilities are: Boy Boy, Boy Girl, Girl Boy, Girl Girl. There are three possibilities with at least one girl. Out of these three, only one has two girls. But my friend says order doesn't matter, so BG is the same as GB. So the probability is 1/2. Which is right?