The diameter of a circle is increased by 50%.The area is increased by

Question

a. 50%
b. 100%
c. 125%
d. 200%
e. 250%

please answer and explain

Answer 1

old diameter: d
old area: pi/4 d^2

new diameter: 1.5d
new area: pi/4(1.5d)^2 = pi/4 d^2 (2.25)

So, new area - old area = 2.25-1 = 1.25 = 125%