Question

The inner and outer radii of a circular ring are 14 cm and 21 cm respectively. Find the area of the shaded portion.

Answer 1

We know:

Area of the circle =

Area of the inner circle =

= r r

= 14 14

= 44 14

= 616

Area of the outer circle =

= r r

= 21 21

= 66 21

= 1386

Area of the shaded portion = Area of the outer circle − Area of the inner circle

= 1386 − 616

= 770