Posted by **ggift** on Wednesday, September 2, 2009 at 7:37pm.

If a polyhedron has 13 vertices and 21 faces, how many edges does it have? I can't figure this one out.

- GEOMETRY -
**MathMate**, Wednesday, September 2, 2009 at 7:50pm
Use Euler's formula which says that

V+F=E+2

where

V=vertices

F=faces

E=edges

For example, a cube has 8 vertices, 6 faces and 12 edges, so

8+6=12+2

- GEOMETRY -
**ggift**, Wednesday, September 2, 2009 at 7:55pm
ok thanks!!

- GEOMETRY :) -
**MathMate**, Wednesday, September 2, 2009 at 8:06pm
You're welcome!

- GEOMETRY -
**qamar**, Friday, May 2, 2014 at 2:55pm
For a given polyhedron, there are 24 vertices and 32 faces. How many edges does the polyhedron have? [Hint: V + F = E + 2.]

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