A merchant has five sacks of gold coins weighing 10, 11, 12, 13, and 14 pounds, though they all look identical. One sack contains counterfeit coins that weigh exactly one pound less than genuine coins. Using a digital scale only once, how can the merchant identify the counterfeit sack?
Take 1 coin from sack 1, 2 from sack 2, 3 from sack 3, 4 from sack 4, and 5 from sack 5. Subtract the total weight from the expected weight of all genuine coins.
Each missing pound corresponds directly to the number of coins taken from that specific sack, revealing the counterfeit source in a single weighing.
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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