Question

If radius of a circle is so increased than its circumference increase by 5% then the area of the circle will increase by

Answer 1

circumference = 2×π×r
0.05 = (r2-r1)/r1 ......r2 = 0.05r1 + r1 = 1.05 r1
% increase in area = (r2^2 - r1^2)/ r1^2
=(r2-r1)(r2+r1)/r1^2
=(0.05)(1.05r1 + r1 )/r1
= (0.05)(2.05r1)/r1
= 0.1025 = 10.25%
10.25% is the % increase in area