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The Monty Hall problem: why switching doors doubles your chances

"You blew it!" a math professor wrote to a magazine columnist. In 1990, she had told a game show player to switch doors, and about 10,000 readers wrote back, most of them to say she was wrong. She was right. Learn the Monty Hall problem: the game, how to count the odds, why the brain sees 50-50, and how much depends on the host.