You have four identical-looking coins, but one is counterfeit and weighs slightly less than the genuine three. Using a balance scale, what is the minimum number of weighings required to guarantee finding the counterfeit coin?
2 weighings
Place two coins on each side of the scale. The lighter side contains the counterfeit coin. Take those two coins and weigh them against each other in the second weighing; the lighter one is the counterfeit.
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: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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