Originally posted by THUDandBLUNDERTurn over the D and the 2. If the card showing D has something other than 3 on its opposite face, you'll have disproved the rule. If the card showing 2 has the letter D on its opposite face, you'll have disproved the rule.
Each member of a set of four cards has a letter of the alphabet on one side and a number on the other. The four cards are placed on a table so that we can see the sequence D, F, 3, 2. You want to find out if every card with a ‘D’ on one side has a ‘3’ on the other side. You are allowed to turn over two cards. Which two cards would you turn over, and why?