Question

If the radius of a circle is increased by 50%, its area is increased by

Answer 1

Answer:

Quite easy ,

A= πr^2

r'= r+r/2 = 3r/2

A' = πr'^2 = π(3r/2)^2 =π9r^2/4

Increase in area = A'-A = 5/4 πr^2

%increase in area = 【 (5/4 πr^2) / A 】×100 = 125%