I'm posting one puzzle, riddle, math, or statistical problem a day. Try to answer each one and post your answers in the comments section. I'll post the answer the next day. Even if you have the same answer as someone else, feel free to put up your answer, too!
Sunday, March 19, 2006
What am I?
I turn around once. What is out will not get in. I turn around again. What is in will not get out.