Question

A circle has an area of 324π cm2. What is the radius? a. 18 cm c. 18π cm b. 36π cm d. 36 cm

Answer 1

a. 18 cm

Explanation:

Area of a circle is given by: A=πr²

where r is the radius and A the area.

therefore we substitute A with the value for the area in the question.

324π=πr²

cancelling the factor π on both sides gives: 324=r²

√324=r

r=18cm

Answer 2

a. 18 cm

Explanation:

We are given that a circle has an area of 324π cm2. We are required to determine its radius. The formula for the area of a circle with radius r units is;

`A=pi*r*r`

We plug in the area given and solve for r;

`324pi=pi*r^(2)\\\\r^(2)=324\\\\r=18`

The radius of the circle is 18 cm