Question

The circumference of a particular circle is 18 cm. In square centimeters, what is the area of the circle? Express your answer as a common fraction in terms of $\pi$.

Answer 1

81/π

Explanation:

If r is the radius of the circle, then the circumference is 2πr. Setting 2π r equal to 18 cm, we find r=9/π cm. The area of the circle is πr^2= π (9/π)^2 = 81/π square centimeters.

Answer 2

81/π square cm

Explanation:

Area can be expressed in terms of circumference by ...

A = C²/(4π)

Filling in the given dimension, you have ...

A = (18 cm)²/(4π) = 81/π cm²