Babylas, Hilary, and Sosthenes have escaped the tower and divided their treasure into three bags. But now they must cross a river, and the boat can accommodate only two men at a time, or one man and a bag. None will trust another with his bag on the shore, but they agree that a man in the boat can be trusted to drop or retrieve a bag at either shore, as he’ll be too busy to tamper with it. How can they cross the river?
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Sosthenes crosses with his bag, leaves it on the farther shore, and returns for Hilary’s bag. He deposits this with his own bag and returns. Now Hilary takes Sosthenes across, drops him on the farther shore, collects his own bag there, and returns. Hilary drops his bag on the near shore, then takes Babylas over. He returns to collect Babylas’ bag for him, and returns again to retrieve his own.
By André Sainte-Laguë. Maurice Kraitchik writes, “Perhaps it is easier to be honest.”
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