The hardest of the eight questions, I think, is this one:
You know that a certain family has two children, and you remember that at least one is a girl with a very unusual name (that, say, one in a million females share), but you can’t recall whether both children are girls. What is the probability that the family has two girls — to the nearest percentage point?
I won't give an answer, and I ask that you don't either -- but think about it; the answer is surprising. (Bialik says he'll be giving the answers next week.)