Question

In an adjoining figure, the area enclosed between the concentric circles is 770 cm-sq. If the radius of the outer circle is 21cm , calculate the radius of the inner circle

Answer 1

Answer:

In concentric Circles The radius of

outer Circle beR and radius of inner

circle be r R=21cm (given)

Then

difference in areas of the circle is

πR^2-πr^2 = 770

πx2 I^2-πxr ^2=770

441π-πxr^2 =770

π(441-r^2)=770

441-r^2 = 770x7/22 =245

r^2 = 441-245-196

r=v196=14

radius of the inner circle=14cm.