I’ve been meaning to write this lesson up for a long time. Finally, here it is, in all its glory. You can check it out below, or find it here on the lessons page.

This trick is an extraordinary introduction to the power of algebraic thinking, and a reminder of what makes algebra so awe-inspiring. When I was in middle school, I used to make up

A video Launch for this lesson is available in two parts. PDF of the lesson is below the videos.

Part 1.
When using as a class launch, stop at 2:45 and let the class come up try to find their own counterexamples.

Part 2
The solution to the magic trick.