Congruent squares are cut from the corners of a 20 in. square piece of tine, and the edges are turned up to make an open box. How large should the squares cut from the corners be in order to maximize the volume of the box?

Answer 1

v = x(20-2x)^2
v' = 4(3x^2 - 40x + 100)
v'=0 when x=10/3