Math Magic Trick

Topics: Arithmetic, algebra
Material: Pencil and Paper
Grades: 4, 5, 6, 7, 8, 9
Common Core: 4.OA.1, 4.OA.2, 4.OA.3, 4.OA.5, 5.OA.3, 6.EE.2, 6.EE.3, 6.EE.4, 7.EE.
3, 8.NS.1, A-CED.1, A-CED.2, MP1, MP2, MP3, MP5, MP6, MP7, MP8

This trick is an extraordinary introduction to the power of algebraic thinking, and a reminder of what makes algebra so awe-inspiring

This trick is an extraordinary introduction to the power of algebraic thinking, and a reminder of what makes algebra so awe-inspiring.

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

Slides mentioned in the video are here: Math Magic Trick Slides

Use just the first two slides to introduce the trick. The later slides provide an explanation/hint of how it works.

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.

This deceptively simple trick can differentiate broadly. Some students can use it to practice arithmetic or get practice with the rules for, say subtracting negative numbers or dividing fractions, or even whole numbers.

It can also be used to highlight the full power of the algebraic toolset. This one is a favorite.