A group of friends who prided themselves on their intelligence set out to have a contest of wits. Each person in turn asked a question, and anyone who volunteered an answer that was wrong dropped out. If no one could answer, the questioner himself had to answer, and if he was wrong, he dropped out. Each dropout had to put $5 into the pot.
Eventually the matter boiled down to Thompson and Brown, and the erudition of each one boiled up so that both were held even for half an hour.
Finally Thompson said, "How does a gopher dig a hole without leaving a mound of sand at the lip?"
Brown thought about that and said, "I can't answer that. However, since it's your question, you had better answer it."