Polynomial/Rational Word Problem

Question

Identical Squares are cut from each corner of a rectangular piece of cardboard, 8cm by 15cm. The sides are then folded up to make a box with an open top. If the volume of the box is 90 cubic cm, and the side of the square is a rational number, what is the measure of the side of the square?

Answer 1

90 = x(8-2x)(15-2x) = volume

for x = 3/2 cm, the sides are 5 and 12

(3/2)(5)(12) = 90 cubic centimeters. 3/2 = 1.5 is a rational number

there may be another solution, between 1 3/4 and 1 7/8, or between 7/4 and 15/8, but it isn't clear if it's rational.