Let the three dimensions of a cuboid be A, B and C, then according to the mean inequality:

ab+bc+ca≥3(abc)？ Cube root,

The left is half the surface area, which is a constant value, and the abc on the right is the volume.

This inequality takes "=" if and only if a=b=c, that is, a cube has the largest volume.

In other words, "two cuboids and cubes with equal surface areas are large."