Students will learn what Platonic solids are, and why there are exactly five of them. The only prereq is knowing that angles around a point add to 360°. They will also learn a bit about the *Mysterium Cosmographicum.* I recommend showing students this video.

Next, give your students these challenges:

- Sum and Differences by NRICH
- A Puzzling Cube by NRICH
- Wonky Watches by NRICH

Conclude by leading this investigation:

Celtic Counting (counting, proof)

by MathPickle