I'll try. Referring to Pi. Every circle, no matter what its size is, has the same relationship between its radius and its circumference (the distance around the circle). It has been determined that this relationship is 22/7, or 3.14159, and is called Pi. For every circle, however big or small, its circumference equals twice its radius times Pi, or its diameter times Pi (the diameter of a circle is 2 times its radius - actually, it's diameter is two radii end to end...) This is expressed as C = PiD C = 2PiR Hope this helps!