You have a cylindrical jar filled completely with water. Without using any measuring cups, rulers, or pouring any water out of the jar, how can you prove mathematically that exactly half of the water remains inside?
Tilt the cylindrical jar until the water line reaches the exact edge of the bottom rim and the opposite top rim.
Because a cylinder is uniform, when tilted such that the water level forms a diagonal line intersecting the bottom edge and top edge, the empty space and the water form identical congruent shapes, proving the jar is exactly half full.
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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