Of course it is 1/3! The topic says there is a girl, probably the first child and the second child. * * * There are three possibilities: male and female, male and female, and only one is female, so it is 1/3. As for the probability of asking each child, it is of course 1/2. For example, if the title is known, of course, that is 1/2. Mathematics certainly conforms to the actual situation. Mathematics and biology cannot conflict at all. The key is that you have to understand the meaning of the topic first.