Question

In the adjoining figure, the area enclosed between the
concentric circles is 770 cm? If the radius of the outer circle
is 21 cm, calculate the radius of the inner circle
​

Answer 1

Answer:

Let the radius of the inner circle be r cm. Then,

(π×21×21)−πr2=770

π(441−r2)=770

722×(441−r2)=770

r2=196

r=14 cm