Slices and area

We can see that the rectangular prism on page 1 is made up of five copies of the 4 × 3 × 1 slice shown. The base area of the slices is 12 m² and the height is 1 m. We have five such slices in the original prism so we have

\begin{align}V &= 5 × 12\\\\ &= 60\ \text{m}^3\end{align}