This is a challenge that will make you think, and can be done and tested with a group of people. All you need is your mind and possibly a group of willing people, cards, and tape.
The objective is to teach problem solving, and practice creating and applying mathematical systems.
Step 1: Materials
-a group of preferably more than 5 people
-tape (for taping cards to peoples' backs)
-a room preferably without mirrors and reflective surfaces
-paper and pencil