Question

The area of a circle is 81π cm ^2 What is the circumference, in centimeters? Express

your answer in terms of π.

Answer 1

18π cm

Explanation:

The area of a circle is πr²

The circumference of a circle is 2πr

πr² = 81π

or, r² = 81

or, r = √(81)

or, r = ±9

But r=—9 is not acceptable .

so, r = 9 cm

Circumference of the circle is

2πr

= 2π * 9cm

= 18π cm

Answer 18π cm