You are shown a set of four cards placed on a table. Each card has a NUMBER on one side and a LETTER on the other side. The first card has the number "3" on it. The second one has the number "8" on it. The third one has the letter "A" on it and the fourth card has the letter "D" on it. So, the visible faces of the cards show 3, 8, A and D, respectively. Which two card(s) must you turn over in order to test the truth of the proposition that if a card shows an ODD NUMBER on one face, then it has a VOWEL on its opposite face?

Question

Quizplus · Accepted Answer

To test the proposition, you need to check if odd numbers indeed have vowels on the opposite side and if cards that do not show vowels do not have odd numbers. Turning over the "3" card checks if an odd number has a vowel. Turning over the "D" card checks if a non-vowel (consonant) does not hide an odd number.

You Are Shown a Set of Four Cards Placed on a Table