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!
Friday, May 05, 2006
What is it?
What is black when you buy it, red when you use it, and gray when you throw it away?