Good Riddles

Question: No matter how terrible things get for the people of the Arctic, they will not eat a penguin.

Why not?

Question: Mary gets in the shower, but surprisingly her hair is not wet when she gets out. How is this possible?

Question: Two is company and 3 is a crowd. What is 4 and 5?

Question: What is the best way to keep your hat from falling off your head?

Question: It takes ten men ten hours to build a certain wall. How long does it take five men to build the same wall?