A merchant wants to weigh an exact amount of grain using a balance scale. He has only a 7-pound weight and an 11-pound weight. What is the minimum number of weighings required to measure out exactly 2 pounds of grain?
2 weighings.
First, use both weights on opposite sides of the scale to measure a difference of 4 pounds (11 - 7 = 4). Next, divide that 4 pounds of grain evenly on both sides of the scale to get 2 pounds.
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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