Chapter 3.3, Problem 61STP

To determine

To calculate circumference of circle.

Answer to Problem 61STP

Option(C)

  $C=4\sqrt{5}\pi \text{ cm}$

Explanation of Solution

Given information:

The area of circle is $20\pi c{m}^2$

Formula used:

  $A=\pi r^2$

  $C=2\pi r$

  $A$ is area of circle

  $C$ is cicumference of circle

  $r$ is radius of circle

Calculation:

Area of circle, $A=20\pi$

Using area formula substitute value of area

  $20\pi =\pi r^2$

On solving

  $20=r^2$

On solving

  $\sqrt{20}=r$

On solving

  $r=2\sqrt{5}$

Using circumference formula substitute value of radius

  $C=2\pi (2\sqrt{5})$

On solving

  $C=4\sqrt{5}\pi \text{ cm}$

Option(C)