Good Riddles

Question: You use me from your head to your toes,
the more I work the thinner I grow.

What am I?

Question: You bury me when I'm alive,
and dig me up only when I die.

What am I?

Question: Crawls over pages and fells wild beasts.
Helps guide you along in your home and on streets.

What is it?

Question: There are two planes. One is going from New York to London at a speed of 600 MPH. The other is traveling from London to New York at a speed of 500 MPH.

When the planes meet which one will be closer to London?

Question: You have 7 tennis balls that are all identical but one of them is slightly lighter than the others.

Using a balance scale and only two separate weightings, how can you find the light tennis ball?