Either increasing the radius or the height of a cylinder by six inches will result in the same volume. The original height of the cylinder is four inches. What is the original radius in inches?
Volume of a cylinder = pi r^2 h
pi (r+6)^2 * 4 = pi r^2 (h+6) eliminate pi
(r^2 + 12r + 36) * 4 = 10 r^2
6r^2 - 48r - 144 = 0
r^2 - 8r -24 = 0 quadratic formula shows r = 4 + 2 sqrt 10 = 10 .32455532