# Thread: Octagonal pyramid/rectangular prism question?

1. ## Octagonal pyramid/rectangular prism question?

What would be the amount of lateral faces for an octagonal pyramid (that goes for the total as well). Also the vertices and edges?

Same question applies for a rectangular prism.

2. The "amount of lateral faces"? Do you mean the number of such faces rather than the area? Of course, you cannot find the area without knowing the size so I will assume you just mean the number. An "octagonal pyramid" has an octagon as base and edges rising from each vertex of the octagon to a single vertex above the base. It has exactly 8 lateral faces. It has 9 vertices and 16 edges.

Note that counting the base, the octagon has f= 9 faces, e= 16 edges, and v= 9 vertices. f- e+ v= 9- 16+ 9= 2, the "Euler characteristic" for all simple three dimensional solids.

I'll leave "rectangular prism" to you. Just find a rectangular box and count!