Answer:
18π cm
Step-by-step 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
