A locked wooden box contains three coins. Exactly one is genuine (correct weight), one is heavier than genuine, and one is lighter than genuine. You have a pan balance and are allowed exactly two weighings. Can you definitively identify the genuine coin?
Yes
Weigh coin A against coin B. If they balance, A and B are both genuine (since there is only one heavy and one light, and they would tilt the scale). If they do not balance, the third unweighed coin (C) is the genuine one. With one more weighing between the remaining suspect coins, you easily identify which is heavy and which is light.
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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