Question

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

Answer 1

Answer:

Area of outer circle=πr^2

=22/7 multiply 21x21

=66x21=1386cm square

area enclosed between circles =770 cm square

so area of inner circle =1386-770=616 cm square

area of inner circle =πr^2=22/7 multiply r^2

616x7/22=r^2

4312/22=r^2

392/2=r^2

196=r^2

r=14 cm