Puzzles
Gardner's two children
Mr. Smith has two children, and at least one of them is a boy. What's the probability that both are boys?
Reveal the answer
It depends entirely on how you learned that fact: 1/3 if you started from every two-child family with at least one boy, or 1/2 if you learned one specific, already-identified child's sex. Martin Gardner posed this in his October 1959 Scientific American 'Mathematical Games' column and later admitted his original wording was genuinely ambiguous.