Bored during a long flight, an eminent scholar leaned over and woke up the man sleeping next to him to ask if he would like to play a game.

"I'll ask you a question," he explained. "If you don't know the answer, you pay me $5. But if I don't know the answer to your question I'll pay you $50."

When the man agreed to play, the scholar asked, "What's the distance from the earth to the moon?" Flummoxed, the man gave him the $5. "Ha!" said the scholar. "It's 400 000 kilometres. Now it's your turn."

The man was silent for a few moments and then asked, "What goes up a hill with three legs and comes down with four?"

The academic racked his brains for half an hour, and finally handed over his $50. "Okay, okay, what is the answer?" he asked.

The man said, "I don't know," handed him a $5 bill and went back to sleep.