Question

in the adjoining figure the area enclosed between the conentric circle is 770cm^2 if the radius of the outer circle is 21cm calculate the radius of the inner circle

Answer 1

Answer:

The area enclosed between the concentric circles is 770 cm

2

. If the radius of the outer circle is 21 cm, find the radius of the inner circle.

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