Help with formulas for circles! Diameter, radius, area and circumference! Please help answer the formulas!?

I need help with these formulas:

What is the formula to finding the area of a circle if all you have to work with is the diameter.

What is the formula to finding the cirfumference of a circle is you only have the radis or diameter?

Please help me, I am confused!!!

2 times radius = diameter d=2r, r=d/2
If you have the diameter divide it by 2, to get r, the radius.
Area = pi r^2
Circumference = pi x diameter

This entry was posted on Thursday, December 17th, 2009 at 1:58 pm and is filed under area formulas. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

3 Responses to “Help with formulas for circles! Diameter, radius, area and circumference! Please help answer the formulas!?”

William B on December 17th, 2009 at 7:03 pm

2 times radius = diameter d=2r, r=d/2
If you have the diameter divide it by 2, to get r, the radius.
Area = pi r^2
Circumference = pi x diameter
References :
2008!! on December 17th, 2009 at 7:10 pm

area w/ only diamter:
just use pi*radius^2
divide the diamter by two and use the formula

circumference w/ only radius or diameter:
use 2*pi*radius
if u are given the diameter, divide it by two and solve
References :
Erin <33 on December 17th, 2009 at 7:38 pm

The radius is half the diameter so you just divide the diameter by two. Then you do Pi X The radius (1/2 diamter) Squared.

Circumference = D X Pi or Double Radius X Pi
References :

Area List