Find the area of a circle

Geometry Level 1

If the circumference of a circle is $20 \pi$ , what is its area?

40\pi

100\pi

60\pi

120\pi

1 solution

Munem Shahriar
Feb 7, 2018

We know that, $C =2 \pi r$

$2 \pi r = 20\pi$

$2r = 20$

$r = 10$

Now the area of the circle is:

$A = \pi r^2$

$A = \pi 10^2$

$A = \boxed{\pi 100}$