You have three closed boxes labeled 'Red Marbles', 'Blue Marbles', and 'Mixed Marbles'. You are told that EVERY box is incorrectly labeled. Without looking inside, you reach into the box labeled 'Mixed Marbles' and pull out a single red marble. Which box actually contains the blue marbles?
The box labeled 'Red Marbles'.
Since 'Mixed Marbles' is mislabeled and you pulled a red marble, that box must actually contain only Red Marbles. The box labeled 'Blue Marbles' cannot contain Blue Marbles (due to mislabeling) nor Red Marbles (which are in the 'Mixed' labeled box), so it must contain Mixed Marbles. This leaves the box labeled 'Red Marbles' to actually contain Blue Marbles.
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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