How much metal is needed to smelt a cubical metal box with outer side 12 inches long if the thickness of its walls should be exactly 3 inches?

Answer: 1,512 cubic inches

Explanation:

To get the length of the inner side of the cube, we multiply the thickness by 2 and then, we subtract the result from the outer side of the cube.

In terms of equation:

(inner side) = (outer side) - 2 (thickness)

Since the outer side is 12 inches and the thickness is 3 inches, then the inner side is given by

(inner side) = (outer side) - 2 (thickness)

= 12 - 2 (3)

(inner side) = 6 inches

Therefore, the amount of metal needed to smelt the cubic box is given by

(Volume of metal) = (outer side) ³ - (inner side) ³

= 12³ - 6³

= 1,728 - 216

= 1,512 cubic inches