The Four-Card Task


If I was to say “All cards with vowels on one side, have an even number on the other side”, what cards would you need to flip over to see if I was wrong or right?

If you said A and 7, you would be right.  But you probably did not.

I didn’t.  I thought that you needed to flip over the A and the 4.  If the A had an even number on the other side and the 4 had a vowel on the other side then the claim is true.

But the other side of the 4 card does not say anything about the claim.  Remember, all cards with vowels have even numbers on the other side.  I did not say that all cards with even numbers had vowels on the other side.  A card with an even number can have anything it wants on the other side.  The same goes for the D card.

The 7 card has to have a non-vowel on the other side in order for the claim to be true.

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