Question

Can someone explain the answer to this problem? Answer: 6 in.

Answer 1

24 cubes, each 8 cubic inches, meaning each 2 inches on a side.  So the dimensions must be even to fit cubes exactly.  Our box with 9 inches is really only effectively 8 inches because that extra inch doesn't help us fit another cube.  

So our total volume:

$24 \times 8 = (8)(4)h$

$h=6$ inches minimum