A. A woman has two children. I'm looking at one of them right now, and it's a girl. What is the probability that the other is a girl?
B. A woman has two coins placed on the table. I'm looking at one right now, and it is showing tails. What is the probability that the other is tails?
I claim that A and B are the identical statistical problem (with obvious assumptions). The answer to the second one is clear.