If the radius of a circle is increased by 35% then, its area increases by

Let r and A be the radius and area of the circle.

⇒ A = πr2 ----(1)

When r is increased by 35%, new area is:

⇒ A’ = π(1.35r) 2

⇒ A’ = 1.8225πr2 ----(2)

∴ % increase in area = ((1.8225πr2 – πr2) /πr2) × 100 = 82.25%