The clue is not always in what moves. Sometimes it is in what remains calm. In this square, a coin falls into the water at a precise moment — and that moment has a signature.
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Riddle statement
In a square there are three fountains that shoot water at regular intervals. One does it every 4 minutes, another every 6 and another every 9. At 12:00, all three raised the jet at the same time.
Later, before 12:30, a visitor sees that only two fountains raise the jet at the same time. On a whim, he throws a coin into the water of the only fountain that, at that moment, remained calm.
Two minutes later, that same fountain raises the stream.
At what time did he throw the coin and in which fountain did it fall?