Take a piece of paper and cut out a perfect circle with diameter 1 inch.

What is the diameter of the largest unaltered coin which may be passed through the hole without tearing it?

(Consider the coin to be very thin, and the paper to be very flexible and tear resistant, but not at all stretchy.)

little less than pi/2 inches

If you were to cut another annular circle around the original circle and stretch it by folding into half a coin just less than half its circumference could be passed.

Posted by Salil on 2006-05-29 12:47:34