Factor Graphs

Sarah Lonberg-Lew of the Adult Numeracy Network and SABES joined us from Gloucester, MA to lead this meeting with me (honestly, I did very little). We explored a diagram that Play With Your Math calls factor graphs. They got the idea from Things to Make and Do in the Fourth Dimension, by the mathematician and educator Matt Parker. (Check out Numberphile for some of his videos.)

The week before the meeting we sent out this teaser:

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A Strange Algorithm

In our first evening meeting, Eric shared a web site that turns pairs of numbers in diagrams. But how does it work?

(This meeting was based on an underground mathematics lesson, Fawn Nguyen’s post and Michael Lawler’s videos. Thank you all!)

I started the meeting by showing the group the Picture This! web site that turns pairs of numbers into a diagram visualization. I asked for a volunteer to give me two numbers, each less than 10. The first suggestion was 3 & 7. I entered the number into Picture This and this diagram was returned.

3 & 7

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Factor Towers

Eric shared activities from a draft lesson on factors, multiples, primes and composites. The lesson is linked in the post if you are interested in using the materials from the meeting. He would love feedback if you use it with a class.


To start off the meeting, Eric put us into groups and gave each group a bag of paper tiles. He asked us to spend a few minutes looking at them and discussing anything we noticed.

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