Question

A square piece of cardboard is to be used to form a box without a top by cutting off squares, 5cm on a side, from each corner and then folding up the sides. if the volume of the box must be 320 sq. sm, what must be the length of a side of the cardboard?

Answer 1

If the square has side x, then the box when folded up has height 5, and a square base of side x-5-5=x-10

5(x-10)^2 = 320
(x-10)^2 = 64
x-10 = 8
x = 18