Question

In the given figure two concentric circle with centre $O$ have radii $21cm$ and $42cm$. If $AOB=60$ Find the area of the shaded region (Use $\pi =\frac{22}{7}$)

Answer 1

The Radius of smaller circle is $21cm$

The Radius of larger circle is $42cm$

The area of Ring is $\pi (R^2-r^2)\pi (1764-441)=1323\times \frac{22}{7}=4158$

The major angle $\angle AOB=360-60=300$

The area of sector in Ring is given as $\frac{300}{360}\times 41583465c{m}^2$