16. Let $S$ be the area of the base of a prism, $h$ its height, and $P$ a given point. If all pyramids with vertex $P$ and lateral faces of the prism as bases are removed from the prism, two pyramids with vertex $P$ and bases coinciding with the bases of the prism will remain. The volume of one of them is $\frac{1}{3} S h_{1}$, the volume of the other is $-\frac{1}{3} S h_{2}$, and the sum of the volumes is $\frac{1}{3} S\left(h_{1}+h_{2}\right)=$ $=\frac{1}{3} S h$, since $h_{1}+h_{2}=h$. It follows that the sum of the volumes of $n$ removed pyramids is $\frac{2}{3}$ of the volume of the prism. (The magnitude of the sum does not depend on the position of point $P$.)
16. If an internal point of some $n$-sided prism is connected to all its vertices, then we obtain $n$ quadrilateral pyramids with a common vertex at this point, the bases of which are the lateral faces of the prism. Find the ratio of the sum of the volumes of these pyramids to the volume of the given prism.