Explain an easy way to estimate the

Question

area and circumference of a circle
if you know the radius or diameter

Answer 1

The radius is 1/2 of the diameter, which is the width all the way across.

Area = pi x radius^2
Circumference = pi x diameter

If you have the radius, you can figure you the circumference.

Circ = pi x 2 x radius

Vice versa for Area if you have the diameter (divide that by 2 and multiply it by pi)

Matt

Answer 2

If I am looking to estimate, I'd just square the radius (times it by itself) then mutiply by 3 for the area.
I'd take the radius times two (or just take the diameter) and multiply by 3 to get the circumference. Since pi is a little over 3, your answers will be a little low but not bad for an estimate.