and you can see that the ribbon is just over 3 times the diameter of 1 circle. This number, called π (or pi), is approximately 3.14. You have shown that the circumference of a circle is π × ...

Around 250 B.C., the Greek mathematician Archimedes calculated the ratio of a circle's circumference to its ... Mathematicians find a closer approximation every year—in 2002, for example ...