Two guardians stand at a fork in the road. One guardian always tells the truth on odd-numbered days and lies on even-numbered days. The other guardian always lies on odd-numbered days and tells the truth on even-numbered days. Today is Tuesday, the 14th (an even day). Guardian A says: 'Tomorrow, Guardian B will speak the truth.' Which guardian is the truth-teller today?
Guardian A
Today is day 14 (even), so one guardian tells the truth and the other lies. Tomorrow is day 15 (odd), when their behaviors swap. If Guardian A is the truth-teller today (Even-Truth/Odd-Lie), then Guardian B is (Even-Lie/Odd-Truth). On day 15 (odd), Guardian B will indeed tell the truth. Thus, Guardian A's statement is true, confirming Guardian A is today's truth-teller.
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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