Another thinking challenge:

Say that a woman and a man (who are unrelated) each has two children. We know that at least one of the woman's children is a boy and that the man's oldest child is a boy. Can you explain why the chances that the woman has two boys do not equal the chances that the man has two boys?

My algebra teacher insists that the probability is greater that the man has two boys, but I think the chances may be the same. What do you think?