Counter-intuitive geometry question on the PSAT
I did not believe this when I first read it: http://mindyourdecisions.com/blog/2015/07/19/this-psat-question-stumped-almost-everyone-attaching-a-tetrahedron-to-a-pyramid-sunday-puzzle/#.VbdkDkJVikp
Read the article, then play with this.
Consider a tetrahedron and a square pyramid whose edges have the same length. If the tetrahedron and the pyramid are attached on a triangular face so the vertices align, how many faces will the new shape have?