In a secret underground vault, a guard speaks only in direct truths on even-numbered hours, and only in absolute lies on odd-numbered hours. If the guard tells you, 'I lie on odd hours, and today is Tuesday,' what hour of the day is it right now?
An even-numbered hour
Analyze the statement: 'I lie on odd hours'. If it were an odd hour, the guard must lie, meaning the statement must be false—but an odd-hour guard telling the truth about lying is a contradiction. Therefore, it cannot be an odd hour. The guard must be speaking the truth during an even-numbered hour.
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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