Three colored envelopes—Red, Blue, and Yellow—stand on a table. Exactly one of them contains a hidden key. Each envelope has a message printed on it: - Red: 'The key is not in this envelope.' - Blue: 'The key is in the Red envelope.' - Yellow: 'The key is not in this envelope.' If only one of the three messages is true, which envelope holds the key?
Yellow envelope
If the key is in Yellow, then Red's statement is true ('not in Red'), Blue's statement is false ('in Red'), and Yellow's statement is false ('not in Yellow'). This results in exactly one true 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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