Question

Find the area of the semicircle having perimeter $36$ cm.

Answer 1

Let $r$ be the radius of the semi-circle.

Then according to the problem,

$\pi r+2r=36$

or, $\frac{36r}{7}=36$

or, $r=7$.

Then the area of the circle is $\frac{22}{7}\times 7^2=154$ cm${}^2$.