How do you find the radius of a circle and finds the circumference C equals 2 pi R and the area A equals PIrsquared and the area of the circle equals 314159?

Answer 1

Given a circle with an area of 314,159; find the radius r.

The area of a circle is determined by the formula π * r2

A = πr2

Because we have a value for A, we substitute

314159 = πr2

We have to get r on one side of the equation, by itself. To do this, divide both sides by π.

( 314159 / π ) = πr2 / π

Simplify

( 314159 / π ) = r2

We need r to be the only thing on it's side of the equation, so we'll take the square root of both sides, and simplify.

sqrt( 314159/π ) = r

This answer is correct, but because we had a value for A, we can get a decimal approximation.

r = sqrt ( 314159 / 3.14159 )

r = sqrt ( 100,000)

r = 316.227766