A box with a square base and no top is to be made from a square piece of cardboard by cutting 4-in. squares from each corner and folding up the sides, as shown in the figure. The box is to hold 324 in3. How big a piece of cardboard is needed?

Answer 1

If the cardboard has side x, the volume is

(x-8)^2*4 = 324

Now it is clear what x is.