A dodecahedron is a three-dimensional figure with 12 faces. The Greek prefix dodeca- means 2 + 10.

The dodecahedron in the picture has 12 5-sided (pentagonal) faces. That's why Dodecahedron Day is on December 5 each year.

Click here to see students celebrating Dodecahedron Day 2004.

Here are some useful resources for Dodecahedron Day 2012:

– Nets for the Platonic solids.

– Two proofs that there are exactly five Platonic solids. One proof is geometrical, and can easily be understood by middle school students. The second is algebraic, and could be used used with advanced high school students.

– Handout for discovering Euler's formula.

Note: If these are not exactly what you need for your classroom, feel free to adapt and use as you see fit.