Quandaries
and Queries 

A dodecahedron has twelve faces, all of which are regular pentagons. Three edges meet at each vertex of the dodecahedron. An interior diagonal is a segment connecting two vertices such that the segment is not an edge or along a face of the dodecagedron. How many interior diagonals does a regular dodecahedron have? Thank you Joshua (1012) 

Hi Joshua, You should answer this in two steps. First you could count how many vertices there are, that will tell you how many pairs you could join in total; from this you then need to subtract the number of segments that correspond to edges and diagonals across faces. Penny 

