What is the percentage change in the volume of a sphere if its radius increases by 20%?

Answer 1

Vo = 4pi*r^3/3,

r + 0.2r = 1.2r,

V = 4pi*(1.2r)^3/3,

(1.2r)^3 = 1.728r^3,

V = 1.728Vo,
V/Vo = 1.728Vo / Vo = 1.728 = 172.8%,
% Change = 172.8% - 100% = 72.8.