« How do you express the area of a triangle as the function of its height?
whats your major area of political study lately? »

What is the diameter of a circle with an area of 81p in2?

What is the diameter of a circle with an area of 81p in2?

4.5 inches

9 inches

18 inches

40.5 inches

By 81 p in2, I assume you mean 81*pi in^2

A = pi * r^2
81*pi in^2 = pi r^2
81 in^2 = r^2
Take the square root of both sides to get
9 in = r

Since the diameter is double the radius,
d = 2*9in
d = 18 in

I hope this helps!

This entry was posted on Sunday, January 24th, 2010 at 2:47 am and is filed under circle area. 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.

One Response to “What is the diameter of a circle with an area of 81p in2?”

  1. By 81 p in2, I assume you mean 81*pi in^2

    A = pi * r^2
    81*pi in^2 = pi r^2
    81 in^2 = r^2
    Take the square root of both sides to get
    9 in = r

    Since the diameter is double the radius,
    d = 2*9in
    d = 18 in

    I hope this helps!
    References :

Leave a Reply