(1/5/2021) Yesterday a student from Canada, B, emailed me a mathematical question about the mathematics of human trafficking. We studied this topic a year ago in the Math Circle course “The Mathematics of Social Change.” I’ll get to B’s question and my answer in a moment, but first I want to share some follow-up thoughts from this course.

Isomorphic problems

“Aw, are we talking about human trafficking again? I don’t want to feel sad,” said F at the beginning of the session following the human-trafficking discussion. I was grateful to F since I wasn’t sure whether to continue that topic or move to something else. Thanks to his comment, I knew what to do.

The planned follow-up activity to the previous week’s was to use US highway maps and graph theory to analyze travel between states. * I asked the group how we could talk about the same mathematical content in a context other than slavery. In other words, how to change the problem without changing the math. The students rose to the occasion with multiple ideas – a car with money falling out of it, something about solar energy, something else about a bus. They wrote these new problems and then we then shifted gears to other topics for the rest of the day.

I’ve been thinking about F’s question ever since he asked back in February.


Once the pandemic hit and my daughter J’s school district switched to virtual learning, several of her teachers assigned projects related to COVID: things like the math and science of disease spread, etc. I was concerned because she and many students experienced increased depression related to the pandemic (isolation, fear, etc – nothing you haven’t heard about or experienced, I’m guessing). Some students I knew became sad and anxious when tackling these assignments. I talked to my friend R, a therapist, about this. R felt very strongly that schools should be a sanctuary away from immersion into pandemic studies, since students were living it at home. She did not think schools should do lessons centered around COVID. R, of course, was looking at this from a mental-health perspective: school as a place of safety when some students were saying that pandemic-related lessons scared them.

OTOH, some mathematicians I collaborate with were advocating strongly for presenting to students the mathematics of epidemiology. Many of their students and students’ families did not have access to accurate information about how COVID spread, how virulence works, the benefits of testing, etc. Here was an excellent chance for natural learning about math in a relevant context.  And for mathematics to be a vehicle to get important health info home to families.

I came up with a grand plan to ask a variety of therapists, teachers, mathematicians, and parents for their thoughts and then to write about it here. Of course I got caught up in the change in lifestyle the pandemic has wrought, so never followed through. J’s school is no longer studying pandemic-related topics, although some schools and colleges are. This morning I asked her to apply her 20/20 hindsight to the matter: she said “it was a good idea (to study this topic) in the beginning of the pandemic but not now,” that the pros outweighed the cons initially only.  

Regarding COVID: I still wonder what the right thing to do is/was in terms of weighing the emotional versus the intellectual/practical impacts.** Regarding human trafficking: can a certain context diminish a student’s enjoyment of mathematics, even make them not want to come to Math Circle? Regarding both: by exploring these topics with students, are we saving lives, which probably trumps all?  I would like to see some discussion, analysis from psychology, and educational research on these questions. Please point me toward it if you know of it. And let me know what your thoughts are.

Graph Theory

In her email about the math of human trafficking, B reported that she was “struggling to apply math concepts to this topic.”  She read in my blog***

“Suppose law enforcement has enough employees to focus on just four cities in the US. How should they choose which ones? M suggested (and the others agreed) that we can choose the cities with the most lines, in other words, the vertices with the most edges. In other words, we could calculate the degree of each vertex on the graph.” 

Her question was “Would you mind explaining why each vertex’s degree on the graph can represent the city with the most lines?” I realized others reading this might wonder the same thing. Here is my reply:

Please let me know if I am misunderstanding your question and answering something else! I suspect that your confusion may come from the terminology that I am using because in this course we were applying the math topic of graph theory, not geometry. There is some overlap in terms between these fields. Are you familiar with graph theory? A good quick intro to it is here: https://www.mathsisfun.com/activity/seven-bridges-konigsberg.html

Also, if you haven’t already, take a look at the photo on the blog post under the heading “Results and Reaction.” Take a look near the center of the image of the boardwork where it says “NY” with the number 6 in a circle. NY indicates the location of New York City. It is, in graph-theory language, a vertex on the graph. There are 6 lines coming out from the NY vertex. Each of these are called edges. These 6 edges/lines indicate flights. Can you see the line connecting NY to Kingston? This line/edge means that one can fly from NY to Kingston on one of the airlines we investigated. Kingston is another vertex (point). The “degree” of the vertex (point) means how many lines (edges) originate there. NY has 6 edges, or a degree of 6, because we drew 6 lines representing flights from NY.

Thank you for reading and thinking about these things! I’m wishing all of you good health in the new year.


NOTES *  This planned follow-up activity is described in depth on pages 87-88 of Mathematics for Social Justice: Resources for the College Classroom.

** I also wonder about the specifics of studying this topic in a public school where students can’t opt out. In my Math Circle on human trafficking, I was able to give trigger warnings to students and their grownups so people could opt out, request that I not cover this topic, or process it at home outside of the sessions.

*** The original blog post is here: https://talkingsticklearningcenter.org/reducing-human-trafficking-through-math/. I had introduced students to graph theory in week one of this course, which I blogged about here: https://talkingsticklearningcenter.org/intro-to-voting-theory/ (scroll down to “Getting away from Numbers”).

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