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.)

The hole diameter is 1 inch. so its radius is 0.5 inch. Folding the paper into half and then by stretching the hole we can insert a coin with diameter equal to half of the perimeter of the hole. so (1/2)*(2*pi*0.5)=pi/2 inch. approx. coin with diameter 1.57 inch will go thru the hole

Edited on July 12, 2006, 4:02 am

Posted by Yosippavar on 2006-06-20 05:53:43