Question

the difference beyween the area of a circle and the square of its radius is 16.8 m2 .find the radius of the circle.

Answer 1

Let the are of circle be 'a' and that of square be 'b'. Let the radius be 'r'.
So,
$a - b = 16.8$
πr.r-r.r=16.8
r.r(π-1)=16.8
r.r=7.84
r=2.8 (Approximately)

Answer 2

HERE is YOUR ANSWER in ABOVE PIC