Three identical locked boxes contain jewels. One box has two rubies, one has two emeralds, and one has a ruby and an emerald. All three boxes are labeled incorrectly (Ruby, Emerald, Ruby-Emerald). You pull one gem from the box labeled 'Ruby-Emerald' and it is a ruby. What is inside the box labeled 'Emerald'?
Two rubies
The box labeled 'Ruby-Emerald' must be either all rubies or all emeralds because it is labeled incorrectly. Since you pulled a ruby, that box contains two rubies. The box labeled 'Emerald' cannot contain emeralds (since all labels are wrong), and it cannot contain two rubies (since that's the first box). Therefore, the 'Emerald' box must contain the mixed pair: one ruby and one emerald.
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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