Question

The area enclosed by the circumferences of two concentric circles is 423.5 sq.Cm if the circumference of the outer circle is 132 calculate the radius of inner circle

Answer 1

Answer:

17.5cm

Step-by-step explanation:

Common area A2-A1=( Pi*R^2 - pi*r^2)

circumference of Outer circle is 132.

circum=2*pi*R

132=2*pi*R

66*7/22=R (pi=22/7)

R=21

now substituting in a2-a1= pi(R^2-r^2)

423.5 =Pi*(21^2-r^2)

423.5*7/22=441-r^2

441-134.75=r^2

r^2= 306.25

r=17.5