A wealthy merchant locks a precious gem inside a heavy chest. The chest has two keyholes, and he gives two identical locks to his business partners, but no keys. How did they secure the chest without mailing keys back and forth?
Partner A put their lock on the chest and mailed it to Partner B. Partner B added their own lock alongside Partner A's and mailed it back to Partner A. Partner A removed their own lock and sent it back to Partner B, who then removed theirs.
By using padlocks sequentially rather than keyholes that need a single key, both parties can secure a container without ever sharing physical keys.
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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