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:

Answer

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

(π×21×21)−πr

2

=770

π(441−r

2

)=770

7

22

×(441−r

2

)=770

r

2

=196

r=14 cm

Answer 2

Step-by-step explanation:

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