If the diameters of a circle is increased by 100% . Its area is increased by?

Original area = π(d/2)²
= (πd²) / 4
New area = π(2d/2)²
= πd²
Increase in area = (πd² - πd²/4)
= 3πd²/4
∴ Required increase percent
= [(3πd²)/4 x 4/(πd²) x 100]%
= 300%