Question

The perimeter of the semi circle protactor is $36$ cm.Find area.

Answer 1

Let $r$ be the radius of the semi-circular protractor

Now, the perimeter of the protractoris

$(\pi r+2r)=\frac{22}{7}r+2r=\left(\frac{36}{7}\right)$

According to the problem

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

or $r=7$

Now. the area $=\frac{\pi r^2}{2}=\frac{\pi \times 7^2}{2}=\frac{11}{7}\times 7^2$

$=11\times 7=77{cm}^2$