Question

There are two concentric circles one with 13 as the diameter and the other has 4 as it's radius , what is the area between two. concentric circles ?

Answer 1

area between them= area of bigger circle - area of smaller circle
                               = ($\pi$R^2 ) - ($\pi$r^2) 
                               = (22/7 x 13/2 x 13/2) - (22/7 x 4 x 4)
                               = 132.78 - 50.28
                               = 82.5 cm^2