A farmer builds a square pen for sheep. He wants to double the area of the pen by extending two adjacent sides by the exact same length. If the original pen had a side length of 10 meters, how many meters must he add to those two sides?
10 * (sqrt(2) - 1) meters (or approximately 4.14 meters)
Original area = 10 * 10 = 100. New area = 200. New side length = sqrt(200) = 10 * sqrt(2). Since the original side was 10, the added length is 10 * sqrt(2) - 10 = 10(sqrt(2) - 1).
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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