A cylinder’s radius is reduced to 2/5 its original size and the height is quadrupled. How has the volume of the cylinder changed?

Answer 1

oldv = pi r^2 h
newv = pi (2/5 r)^2 (4h) = pi * 4/25 r^2 * 4h = 16/25 pi r^2 h = (16/25) * oldv