Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the other doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Do you keep door No. 1 or do you make the switch to door No. 2?¹

--pages 180-181, Randomness
1. This now infamous problem was originally appeared in the September 1990 Parade column, "Ask Marilyn," where Marilyn vos Savant was asked the question by a reader. The problem is named after the host of Let's Make a Deal, Monty Hall.

Return to BRAINTEASERS