Card Hypothesis Puzzle

FACT: Each card has a number on one side and a letter on the other.
HYPOTHESIS: Every card that has a vowel on one side has an even number on its opposite side.

THE TEST: Which card or cards must you turn over in order to test the Hypothesis?


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The 15 possible answers are:

All four cards: A B C D
Three cards: A B C / A B D / A C D / B C D
Just two cards: A and B / A and C / A and D / B and C / B and D / C and D
Just one card: Card A only / Card B only / Card C only / Card D only

43 thoughts on “Card Hypothesis Puzzle”

  1. I think that Card A and Card C should be turned over. This will test the hypothesis because they are the cards with a vowel and an even number.


  2. All 4 Cards need to be turned over to see if there is an even number behind E, and odd behind G, a vowel being 2, and a consonant behind 3.


  3. A and D. Those are the only cards with which to falsify the hypothesis. If A (E) has an even number and D (3) a consonant, the hypothesis stands. Cards B and C prove nothing either way – at most they confirm a bias.


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