You are shown four cards laying on a table showing '3', '8', 'Red', and 'Blue'. Each card has a number on one side and a color on the other. Which card or cards MUST you flip over to test the rule: 'If a card shows an even number on one side, then its opposite side is Red'?
The '8' card and the 'Blue' card.
To test 'If even, then Red', you must check '8' to confirm its back is Red. You do not need to check '3' (odd numbers are irrelevant to the rule) or 'Red' (an odd number on its back doesn't break the rule). However, you must check 'Blue' because if its back is an even number, the rule is disproven.
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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