Question

A rectangular box is 3 feet wide, 6 feet long, and 4 feet tall.

Answer 1

To find how much space remains in the box, you will find the total space of the box by finding the volume of it.  Then you will subtract the volumes of the 2 triangular prisms.  The remaining would be the extra space.

Volume of Rectangular Prism  -  2(Volume of the Triangular Prism)
Bh                        -                     Bh
(3 x 6 x 4)             -                   2 [(1/2 x 2 x 5) x 3]
72 cubic feet     -                 30 cubic feet
42 cubic feet

There are 42 cubic feet of space remaining.