Four sealed envelopes are labeled 1, 2, 3, and 4. Exactly one envelope holds a cash prize. Each envelope has a clue written on it: Envelope 1: 'The prize is in an odd-numbered envelope.' Envelope 2: 'The prize is in Envelope 2.' Envelope 3: 'The prize is not in Envelope 1.' Envelope 4: 'The prize is in Envelope 3 or 4.' If exactly three statements are true and one is false, which envelope holds the prize?
Envelope 3
Testing each possible location: If the prize is in 3, Envelope 1 is True (3 is odd), Envelope 2 is False, Envelope 3 is True (3 is not 1), and Envelope 4 is True (in 3 or 4). This gives exactly 3 True statements and 1 False statement.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Hard. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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