Question

In the adjoining figure the area enclosed between the concentric circles is 770 CM² square if the radius of the outer circle is 21 CM calculate the radius of the inner circle​

Answer 1

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

Let the radius of the inner circle be r cm. Then,(π×21×21)−πr2=770

Let the radius of the inner circle be r cm. Then,(π×21×21)−πr2=770π(441−r2)=770

Let the radius of the inner circle be r cm. Then,(π×21×21)−πr2=770π(441−r2)=770722×(441−r2)=770

Let the radius of the inner circle be r cm. Then,(π×21×21)−πr2=770π(441−r2)=770722×(441−r2)=770r2=196

Let the radius of the inner circle be r cm. Then,(π×21×21)−πr2=770π(441−r2)=770722×(441−r2)=770r2=196r=14 cm