Skip to content # Intersection Math

## Activity Guide

# This guide looks at the session and explores intersection math in detail.

Tanton, James. (2020). Intersection Math. In S. Kohli (Ed.), Math Circle Activity Database. American Institute of Mathematics. https://mathcircles.org/activity/intersection-math

Contributor(s): James Tanton

Math Circles: MTC Network

- Activity Description
- Topics Covered
- Session Styles
- Mathematical Practices

What is four times three? 12 you might say, but no longer! In a new type of math — intersection math— we will see that four times three is 18, two times two is 1, and that two times five is 10 (Hang on! That’s not new!) Let’s spend some fun time together remembering what it is like to figure things out for the first time, rekindle that joyous creative mathematical spark in each of us, and realise that we are each capable of ingenious and clever thinking. Let’s work out 1001 x 492 in intersection math together!
The key to unlocking this exploration is to organise data in a table and observe some remarkable structure. Next, to use the patterns observed to guide logical reasoning for them.