To Calculate the Edges of a Polyhedral

I’m sure this math is trivial to most statisticians, physicists and mathematicians, but some friends and I determined how to calculate the edges of any 3 dimensional polyhedral. We used my AD&D dice to verify.

(E * F) /2

where

E = the number of edges on a single face of the shape, and
F = the number of faces on the shape.

For example, a six-sided die has 12 edges, a 20-sided die has 30 edges.