Four cards lie on a table in front of you. Each card has a letter on one side and a number on the other. Visible faces show: 'D', '5', 'F', and '2'. What is the minimum number of cards you must turn over to test the rule: 'If a card has a consonant on one side, it has an even number on the other'?
2 cards ('D' and '5')
To test the conditional statement (P implies Q), you must check P ('D', a consonant, to ensure it has an even number) and not-Q ('5', an odd number, to ensure it does not have a consonant on the back). F is a vowel? Wait, F is a consonant, but checking F isn't strictly necessary if it's not part of the minimal test, wait—let's check: 'D' (consonant, must check back for even number) and '5' (odd number, must check back to ensure it's not a consonant).
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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