Question

find the area enclosed between two concentric circle of radius 3.5 cm and 7cm. A third concentric circle is is drawn outside the circle of 7cm so that the area enclosed between it and the 7 cm circle is the same as that between the two inner circle. find the radius of the third circle correct to one decimal place

Answer 1

Answer:

Given,1st circle radius =3.5 cm(r), another circle radius= 7 cm

(R)

Formula to find the area of a circle =πr^2

Greater circle area - Smaller circle area = Area between the two circle

=πR^2-πr^2        (π= 22/7)

=22/7 x (7)^2- 22/7 x (3.5)^2

=22/7 x 14 - 22/7 x 7

=22 x 2 - 22

=44 - 22

= 22 cm