Maybe it's easier to think about like this: if you always switch, you only lose if you picked the door with the car first. That's a 1 in 3 chance to lose. (And a 1 in 3 chance to win if you never switch).
--Solo
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You said you wanted to be around when I made a mistake; well, this could be it, sweetheart.
Comment on Re^7: Marilyn Vos Savant's Monty Hall problem