Here is a really interesting, “messy” math puzzle problem:
Say you have 16 two-sided puzzle pieces that fit together into a circle. Each puzzle piece has either two “in” knobs or two “out” knobs. Eight of these 16 pieces have two “in” knobs and the remaining pieces have two “out” knobs. See picture.
In how many ways can this puzzle be made?
This beautiful math challenge is by Justin Solonynka.