Three boxes—Red, Blue, and Green—stand on a table. Only one contains a brass key. Red's label reads: 'The key is in this box.' Blue's label reads: 'The key is not in this box.' Green's label reads: 'The key is not in the Red box.' If exactly one label statement is true, which box holds the key?
The Blue box.
If the key is in the Blue box, Red's label is false ('Key in Red'), Blue's label is false ('Key not in Blue'), and Green's label is true ('Key not in Red'). This results in exactly one true statement. Any other key location produces two true statements.
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: Easy. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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