Three suspects—Arthur, Bob, and Charlie—are questioned about a stolen item. Arthur says: 'Charlie is guilty.' Bob says: 'Arthur is innocent.' Charlie says: 'Bob is lying.' If exactly one suspect is guilty, and the guilty suspect is the ONLY one who lies, who is guilty?
Charlie
If Charlie is guilty, he lies ('Bob is lying' is false, meaning Bob tells the truth). Arthur is innocent and tells the truth ('Charlie is guilty' is true). Bob is innocent and tells the truth ('Arthur is innocent' is true). All conditions are satisfied consistently.
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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