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Archiving Links from 21st Century Math

I did a 4-week math teacher professional development this summer: 21st Century Math 2025. I participated in it also in 2023, its first year, and really loved it. I highly recommend it for math teachers who love math, but haven’t played around with math puzzles or exploring novel mathematics themselves in a while. As Fawn Nguyen put it in our closing session (she was a featured speaker), she said this kind of work “nourishes us” as teachers. I truly felt that and loved that description.

It is a “choose your own adventure” model where we have lots of options of how to engage. I focused my attention on working on the problem sets and attending zooms from various research mathematicians who were talking on their research related to the problem sets. Because of my summer schedule this year, I didn’t dedicate myself in the same structured way that I did in 2023 when I felt like I mined a lot of the content. Here, I did some deep dives into much (but not close to nearly all) of the content, and I wasn’t able to make all the zooms or create/give an end-of-program presentation. Still I feel like I got a lot out of it.

Participants communicated on a Zulip site (like a discord server). I wanted to archive some of the links that participants shared on that site, since it will force me to go through everything posted, and also collect all the links I think might be helpful in the future where I can access them all in one place. It’s a bit of a hodgepodge of things.

Articles/Books and Interesting Problems:

One participant posted: “I’m interested in making ways for people outside universities to engage with current maths research (recently I put together this puzzle x article that folks here might be into!)” [and here are all of their science/technology articles] 

Someone asked for a good book to teach themselves some number theory, and someone else responded with the book written by a math tiktok-er I like! It’s free online, which is awesome, called “Number Theory and Geometry.” A quick skim makes it feel accessible, which doesn’t surprise me from their tiktoks! Another highly recommended “An Illustrated Theory of Numbers” which isn’t free, but the preview looks really lovely and up my alley since I love concrete and visual learning.

One interesting problem that was shared was the Sword of Knowledge: “A sword of knowledge can slay the Dragon of Ignorance, who has three heads and three tails. With one stroke, slayers can chop off one head, two heads, one tail, or two tails; however, the consequences lead to a variant of the structure. In order to successively slay the Dragon of Ignorance, Students must exercise strategic analysis when fighting this creature.” And what’s really lovely is that the website has a lot of great “math fair problems” which seem like fun, rich, and investigative problem solving tasks.

Living Mathematicians/Mathematicians Stories

Annie Perkin’s “Mathematician’s Project“

Living Proof: Stories of Resiliance Along the Mathematical Journey

Meet a Mathematician:     https://www.meetamathematician.com/home

Her Math Story:  https://hermathsstory.eu/

Mathematically Gifted and Black:  https://mathematicallygiftedandblack.com/

Indigenous Mathematicians:  https://indigenousmathematicians.org/

Latinx and Hispanics in Mathematics: https://www.lathisms.org/posters

The PD organizer also shared: “Here are a couple of short videos related to this thread; they recently popped up in my social media. They are clips of interviews with two Oxford undergraduates studying maths. I particularly like what Ellie says in Part 2 about “You realize that you’re right for being confused, and that anybody at any stage who acts as if they understand what’s going on with maths has no idea what’s going on.” Sometimes it’s our students who are trying to actually understand what’s going on are the ones we think are “struggling”.

Part 1: https://www.youtube.com/shorts/B2O6S_BWkyI
Part 2: https://www.youtube.com/shorts/3cie4VnHeC0“

Math Communities:

Another participant is heavily involved with the Julia Robinson Mathematics Festival (JRMF).  They shared about two online math teacher community that grew out of this world they are involved in:
“JRMF Community Math Circle: After running math festivals all over the world, JRMF pivoted in March 2020 to offering a weekly online math circle.  I joined as a volunteer for a couple of months and then as an employee for a year.  Being part of a community of people with similar interests all over the world was a silver lining to the pandemic for many of us.  
When JRMF went back to doing in-person events, some of us volunteered to keep the math circle going as a monthly event.  We are always happy to have more volunteers.  The math circle meets on weekends at 11 am PT, and for the two weeks prior to each math circle, we hold 90-minute trainings – exploring the topic and discussing pedagogy for it.  You are welcome to come to observe a math circle and/or come to a training to find out about it.  Even if you join as a volunteer, there is no obligation to volunteer any particular month – you just sign up for when you can.
We are currently on a 2-month summer break but will resume in September.
Puzzles & Pedagogy: The other is a weekly event that is kind of like a math circle for adults.  It’s called Puzzles & Pedagogy and is run by Gord Hamilton of Math Pickle.  Topics vary in level and the balance between puzzling ourselves and discussing pedagogy also varies.  It meets weekly on Thursdays 12:30–2:00 PT and is also free and no-obligation.  
Both Math Pickle (MathPickle.com) and JRMF (JRMF.org) are also great resources for teaching – at any level!”

In response to that, another participant shared that they found an online Math Teacher circle, CAMI (Community of Adult Math Instructors). I’ve always wanted to participate in a math circle, so I’m hoping to join one of them! Here’s a flyer they link to, with a bit of information.

LaTeX:

For using LaTeX in MS Word, here’s a 1 minute video on how to do that. And here’s a comprehensive beginner’s resource for LaTeX and a place where you can draw a symbol and it spits out the LaTeX code for that symbol.

The PD organizer also gave these resources: “Overleaf is an online platform for writing documents in LaTeX. It’s like Google docs but for LaTeX. It also has a lot of document templates, very handy. It’s free for individuals, but there’s a subscription fee if you want to collaborate with others. https://www.overleaf.com/

In actual Google docs, you can go to Extensions and the Add-ons and install something called Auto-Latex Equations. This will let you type LaTeX formulas within your Google doc.

If you’re on a Mac, you can (like me) use TeXShop to compose LaTeX documents. It’s a free downloadable program. https://pages.uoregon.edu/koch/texshop/

If you just need a snippet of LaTeX as an image, there are a number of website that can help you out. Here’s one: https://www.quicklatex.com/

Also worth knowing: if you have Keynote, LaTeX is a native feature! Just go to Insert and then Equation, type your LaTeX (no dollar signs required), and hit Insert, and you get a beautiful math expression that is scalable, etc.”

Soap Bubbles: These were one of the research focuses for the program

In one of the presentations, a researcher shared how he made the soap bubbles to illustrate his ideas: “To make these planar soap bubbles, you just need a shallow pan of some kind. I used the lid of one of these, because it’s what I had lying around. A baking sheet with raised edges, for example, should also be fine.

Then you need a sheet of acrylic. I got one from a picture frame. It needs to be big enough to balance on the raised edges of the shallow pan, so that it’s raised off the bottom a little (like, a cm or 2). Then you add water and dish soap to the pan, and use your hand to spread some on the underside of the acrylic. Put the acrylic on top of the pan and use a straw to blow bubbles in the gap between the pan and the acrylic. That’s it! If the bubbles pop when they hit the acrylic, spread more bubble mix on the underside.

I find that the bubbles are very visible in person, but they don’t show up well on cameras (or on zoom). If that’s what you need, adding a bit of food coloring to the bubble mix helps.”

Quanta article “‘Monumental’ Math Proof Solves the Triple Bubble Problem and More” (the bubble problem was one of the big problems we were working on this summer)

A record of conference takeaways — TCM 2024

On Thursday, after school, I hopped in an Uber to the airport. I was flying to a conference, the “Teaching Contemporary Mathematics” conference (TCM) held at the North Carolina School of Science and Mathematics. I think I’ve been at least twice over my career, maybe three times, and always found it to be a really solid conference. The big sell for me is that it’s primarily high school math-focused, and most of the sessions are given by actual math teachers about their own teaching practice. And more importantly, it’s felt like forever since I just got to geek out with other math teachers. A fellow teacher from my school and I arrived pretty late and just passed out, with dreams of conference day on Friday.

Although I haven’t blogged in forever, I wanted to at least outline a few things tonight that I can return to. But it’s late and I’m tired, so I’m only going to do a few tidbits.

There were two sessions that got the mathematical side of my brain whirring.

Ryan P gave a talk on “A Rainbow of Random Digits,” where he went from 1D to 2D to 3D to think about a interesting problem. I thought what he showed was beautiful, especially for the 1D and 2D which I could see using with students in a sort of ongoing independent study/investigation. For the 1D question, he asked us if we had two dowels, of length 1 and length 2, and we split the larger dowel into two pieces, what is the probability that the (now three) dowels could form a triangle. A nice fun introductory question with various approaches to answering it. For the 2D question, he asked as a warm up: if you had two numbers chosen randomly between 0 and 1, (a) what is the probability that the sum is greater than the product, and (b) what is the probability that the sum of between 5 and 6? Lovely scaffolding, and the first question requires a little bit of calculus, which is fun. And then the full 2D question (which can be answered using some calculus, but I think it’s even more beautiful without it): if you have two random numbers between 0 and 1, what is the probability that the first non-zero digit of their ratio is a 1? a 2? 3?… 9? Totally fascinating 2D probability space, with lots of “triangle slivers.” To whet your appetite, here it is:

And totally not my intution, but the probability of getting a 1 (33.3%) is greater than the probability of getting a 2 (14.9%) which is greater than the probability of getting a 3 (10.2%), etc. The calculation involves some fun infinite geometric series. All of this was new to me. I also have no idea why getting a 1 digit is more likely than getting a 2 digit which is more likely than getting a 3 digit, etc. My intuition–which was way off–made me think all digits would be equally likely. Now honestly, I don’t know how teachers can actually build something like this problem into their normal classroom practice, but I do know that I’d love to work with a student to get them from the statement of the question to the answer in a lovely set of independent investigations, and some well-thought-out hints to guide. (And maybe chatgpt to write some simple code to do an initial simulation.) My friend and colleague suggested that maybe the distribution might be related to Benford’s law.

The second session that got the mathematical side of my brain whirring was by Bryan S. He had first learned about Conway’s “Rational Tangles” a few years ago, and wanted to present it to us. Wonderfully, I had first learned about these from Conway himself when I was in high school attending Mathcamp (and Conway was a guest lecturer). Conway was an electric speaker — and this one lecture of his imprinted itself on my mind. Now skip forward to this year. I had students work on “Explore Math!” projects and one worked on knot theory. I mentioned in my feedback to one student I had a really cool knot theory-adjacent thing I learned and I could show her. She responded saying “yes, please!” Of course it’s been years since I learned Rational Tangles. And it’s like the universe said “Oh, let me bring Bryan S. to you to remind you about all the nitty gritty of it.” And he was fabulous — a marvelous instructor who somehow managed to convey the excitement, weirdness, inquiry, all in a single short session. The crux of the setup is that you have two ropes held by four people:

There are two moves: T(wist) which has the front right person and back right person switch positions, where the front right person brings their rope under the back right person’s rope, and R(otate) where the four people just rotate clockwise. It turns out that by doing seqences of moves like this, such as TTRTRTTRT (etc.), you can get a pretty tangled tangle in the middle of the two ropes. One question — the main one we talked about — is if you can do a series of Ts and Rs to “undo” the tangle and get back into the original position of just two untangled ropes. Amazingly, a few Mathcampers created a digital version of this twisting and rotating and it took me about 20 minutes today to find it even though I knew it existed and I had played with it before. Here it is!

Another session I went to was Chris B’s Estimathon! I participated in my first estimathon at the Park City Math Institute many years ago (and again, a couple years ago). I hated it both times, for a few years. First, I hate estimating. I love thinking and calculating — but Fermi problems? I get really annoyed because I feel I rarely have the adjacent information that can unlock the problem. Second, the other people (both on my team and on all the other teams) were very, very competitive. I prefer a cooperative board game over a competitive board game, and in this, I think I feel similarly. That being said, I really enjoyed doing the estimathon with Chris and our other math conference participants. It was fun because the other people on my team were chill about it, and also let me sort of work alone at times when I got obsessed with a problem. Here are two example questions we were tackling:

Yes, I went to #5 because you can calculate that. Here’s what the scoring sheet looked like:

So you get to guess a minimum value and a maximum value for the range that the answer is in. And your score is ceiling(maximum/minimum). In other words, take the maximum value, divide it by the minimum value, and round up. So min: 2000, max: 3000 would yield a score of 2, and min: 2000 max: 4000 would also yield a score of 2…. but min: 2000, max: 4001 would yield a score of 3. Your goal is to get the lowest score. At the end, Chris gave us the absolute best idea (which I think he got from his colleague Emily). You have kids find out numbers for something that they are passionate about or would be an expert in. It could be “the number of pokemon” or “how many grandchildren does Sameer’s father have?” And then later in the year, you could create an estimathon out of these numbers — where kids have to see what they know about each other and their passions. I love this as a way for people to get to know each other.

There were two additional sessions that I attended, which were about students and math, and I loved both. First was by Jenny W, Lauren B, and Kevin J, and reminded me of the “5 practices” (https://www.nctm.org/Store/Products/5-Practices-for-Orchestrating-Productive-Mathematics-Discussions,-2nd-edition-(Download)/). It’s about using Desmos to highlight and discuss student thinking and to uplift student brilliance. Although I’ve seen many, many presentions on the 5 practices over the year (especially at PCMI), this was a great reminder of a lot of the things I don’t know, and teacher moves I’ve stopped flexing.

The second was by Lauren B called “I am, We are, You are.” It highlighted a few things to me. First, there’s a gap between the demographics of people who teach mathematics (and their identities) and the population of students who learn math (and their identities). She posed a question (of which she thinks the answer is yes): “Is there a way to expand identity in a math class?” I think this is a great question to chew on — and not easy. Especially if you take away classes like statistics or data science from the mix. We played with a super engaging Desmos activity which gave us choice on which data sets to plot against each other, and the fun part was guessing what the scatter plot would look like before we saw it. And she had a quote from Rochelle Gutierrez (who I’ve met before briefly!) which I couldn’t copy down quickly enough, but went something like “Do I have to be a better you in this classroom, or can I be a better me?” This is a student asking the question — essentially saying “Do I have to mold myself to be a miniature version of you, the teacher, to succeed in this room we’re in together?” I also thought that had a lot to chew on… in terms of what we expect from students and the culture that we build together.

Okay, it’s now 9pm and I’ve been at this for way longer than I intended, so to sleep I go.

***

It’s the next day and the conference has finished and I wanted to archive — briefly — the remaining sessions.

First, Hollylynne L. gave the keynote talk “Data Science is Everywhere and For Everyone.” Some takeaways for me are that there are a few large organizations (like NCTM, NCSM, ASA, etc.) that are collaborating to create a united data science position. It’s drafted, and about to be adopted, and has four guiding principles: (1) data science is contextual and multidisciplinary, (2) data science is an investigative process, (3) data science understanding and experiences are for everyone, and (4) data science educators must develop and practice ethical uses of data. The presenter shared her experience ethnographically observing data scientists for 9 months and what traits they exhibited. Then she shared with us that she feels like data science needs to be presented to kids with larger data sets — in terms both of cases but also in number of attributes shared (e.g. not just a survey with one or two questions, but a survey that has a ton of questions!). As an expert on CODAP, she shared how to fluently use it to show data, ask questions, and then interrogate the data. That part was inspiring, and in only a few minutes showcased the power of CODAP (codap.concord.org). Her talk also got me thinking about how our department has over the years shoved all of data science/statistics to our AT Statistics courses as we were making room for everything else we need to teach. Lastly, at the end, she shared a resource I want to follow up on called InSTEP. It is a free online site [https://instepwithdata.org/public/] that is designed to get teachers ready to teach data science and statistics, and it sounds like you learn lots of content, pedagogical moves, and you learn to use various tech tools but primarily CODAP (which is what I want to learn). So yay!

My next session was by Reed H and was an invigorating conversation on Standards Based Grading. He presented a “post mortem” of him implementing SBG in his precalculus classroom for the first time, sharing why he made the switch but also the tradeoffs that occurred. Although our school is moving in a different direction, I was still curious to see how the SBG conversations were going — and it reminded me how much I liked SBG even though it took me 4 years until I had refined it to the point where I could run it fluidly in my standard calculus classes. Reed’s own observations, and the conversations we had as small and large groups, also reminded me of my own path to SBG, and how I now know there is no single flavor of SBG that is going to work for all, because its success is dependent on so many cultural and institutional factors. And there is no magic bullet that is going to make it suddenly easy.

My last session was by Verónica Z and Doru H and was on Linear Programming and Other Means of Optimization. The presenters shared three ways to do optimization without calculus. First, the standard linear programming. The second was something called the “simplex algorithm.” Honestly, I got very confused at this point, because it isn’t in any way intuitive and I think that part of the presentation was meant for people who knew the method. So I ended up stopping my notes and writing “very confused” on my page. (I did find this example that went through the algorithm that I’m curious to read though, to get the crux of the algorithm, but don’t think it will explain “why” it works.) Finally, we learned the TOPSIS algorithm which was just invented in 1991 (“Technique for Order of Preference by Similarity to Ideal Solution”). New math! And the presenter, Verónica, did a really cool job of showing us how to make a decision of which new phone to buy (out of a choice of three) if we were looking at two variables: picture quality and battery life. It’s such a simple algorithm that — at the highest level — has you develop two new “fake” phones that exist — the best phone and the worst phone — one with the best of the traits of the three phones that exist and one with the worst of the traits of the three phones that exist. We plot all three phones and the best “fake” phone and worst “fake” phone. And then we find the “distance” from each of the three phones to the best and worst “fake” phones, and use those distances to rank the phones. Details are in my notes, but I loved learning new math in the universe, and new math to me!

Lastly, the conference was raffling off math art, and although I didn’t win, a new friend did, and she saw how much I coveted them and offered me hers. I demurred and then eventually accepted.

***

Personal Note: Speakers for the most part shared their slides with attendees. So I’ve downloaded the sessions I went to and saved them on my google drive. But I don’t know if they are officially public, so I’m just linking to them here for my own easy access.

Archiving an Idea for the Future: Reading and Writing About Mathematics

I had a thought that just occurred to me and I wanted to archive it before I forgot it. I’ll probably forget that it is even here at all, and nothing will come of it, but I had a thought about developing a new one-semester course for juniors and seniors at my school.

It would be called something like “Reading and Writing about Mathematics.”

I’ve always been obsessed with reading books that aren’t textbooks about mathematics. I have almost half a bookshelf filled with these books. I love (when I have time) reading articles about modern mathematics in Quanta magazine. I’ve sometimes formally incorporated reading books about math in my classes in the distant past (a variety of books and articles in multivariable calculus; a book called Weaponized Lies: How to Think Critically in the Post Truth Era in my Algebra 2 class). And for many years, I’ve reached out to kids and set up many math book clubs, where we meet over lunch for a few different times to read books about math. I even was once interviewed about this, and wrote an article about this.

So why not formalize this into a class?

The biggest benefit I can see for the class would be introducing students to what modern mathematics is, so they don’t leave thinking mathematicians are just doing precalculus or calculating integrals in their ivory towers. Just like kids in physics will learn that the physical world is weird and wild when they are introduced to the ideas of quantum mechanics and relativity (even though they aren’t delving into the nitty gritty) in high school, I’d like a way for kids taking this class to learn that the mathematical world is weird and wild… and most importantly: human. A course like this will humanize math for students.

Right now I’m reading Jordan Ellenberg’s book Shape: The Hidden Geometry of Information, Biology, Strategy, Democracy, and Everything Else [here], with 5 students and 2 other teachers. As we’re reading it, there are parts that intrigue students but we need to parse it out together for it to fully make sense. One example was in this book, Ellenberg talked about the question “How many holes does a straw have?” and he brings us into topology and understanding how holes can have various dimensions. As we parsed this, I thought: oh, reading this and then also doing some mini-problem sets on the math could help kids understand things at a deeper level, or confirm their understanding of what they read. We could do our own simulations of random walks, in the section involving that idea. We could parse out the idea of the “necklace problem” which we’re going to talk about at our next meeting, which I’m sure the kids won’t understand because they aren’t drawing things out but more passively reading. In other words, we’d be able upgrade a passive reading of the book to an active reading of the book with a mini-problem set that brings ideas that might not fully make sense to life.

Additionally, there are books or articles that we could read that would help students understand the social construction of mathematics (hello anything on the controversy of the ABC conjecture and Mochizuki’s “proof”).

We could learn about the origin of ideas that seem to have existed forever or that we take for granted, but actually had to be developed (e.g. the idea of “0” or the controversy over calculus being on firm footing). And mind-blowing ideas like how all of mathematics almost fell down with the work of one mathematician, Godel. And we can learn about marginalized and overlooked people. There are some really great children’s books on mathematics, so we could read some of those as we begin the class! Maybe complement that with some excerpts from Douglas Hofstader’s Godel, Escher, Bach, a newspaper article about a modern mathematical breakthrough, some math poetry, a formal mathematical paper that has come out in the past 10 years and is hailed as one of the most important discoveries, and one more piece that’s maybe more traditional, so kids can see the wide variety of ways people write about mathematics.

And kids would think about how the writing that they’re reading is effective to reaching their intended audiences, or how it isn’t effective and what would make it better.

And kids could pick ideas or people to learn about, do their own research, and write their own popular mathematics writing. We can workshop it and publish a little journal at the end of class with our pieces.

I could reach out to English teachers to learn how they facilitate conversations about books so that it doesn’t go stale (we aren’t doing the same thing every time we discuss some of the reading). I’m sure there are universities that offer similar classes, so I could see what else is out there. And I know MIT has a graduate program in science writing that I could draw ideas from.

Okay, I’m done brainstorming for now. I just wanted to get all these ideas out before I forget them. I might update this post with additional ideas as my mind percolates. As I said… most likely nothing will come of this. But I could see having a really fun summer trying to put this course together.

NOTE: The deadline has passed to propose this course for next year. But it would take me a long time to develop the course outline anyway, so I could try to design it this upcoming summer and submit it for the following year.

I’m not sure this is comprehensive, but this is a list of books I’ve worked with kids/faculty in various capacities on [but it is not all the popular math books I’ve read]

*=I’ve done this for a student (or student and faculty) book club
**=I’ve led/organized a book group with just teachers on this
***=I’ve had students individually read this (to discuss with me in an independent study or for a math project)

*Anna Weltman, Supermath [here]
*Edwin Abbott, Flatland [here]
**G. Polya, How to Solve It [here] 
*Amir Alexander, Infinitesimal [here]
***Charles Seife, Zero: The Biography of a Dangerous Idea [here]
*G.H. Hardy, A Mathematician’s Apology [here]
***David Leavitt, The Indian Clerk [here]
*Steven Strogatz, The Calculus of Friendship [here]
**Steven Strogatz, Infinite Powers [here]
*Edward Frenkel, Love and Math [here]
*Robert Kanigel, The Man Who Knew Infinity [here]
***James Gleick, Chaos [here]
***Yoko Ogawa, The Housekeeper and the Professor [here]
*Margot Lee Shetterly, Hidden Figures: The American Dream and the Untold Story of the Black Women Mathematicians Who Helped Win the Space Race [here]
***Hiroshi Yuki, Math Girls talk about Integers [here]
***Hiroshi Yuki, Math Girls [here]
*Jordan Ellenberg, How Not To Be Wrong: The Power of Mathematical Thinking [here]
*Jordan Ellenberg, Shape: The Hidden Geometry of Information, Biology, Strategy, Democracy, and Everything Else [here]
*Daniel Levitin,Weaponized Lies: How to Think Critically in the Post-Truth Era [here] — the first third
***Ben Orlin, Math With Bad Drawings [here]
*Ben Orlin, Math Games with Bad Drawings [here]
***Paul Lockhart, A Mathematician’s Lament [here]
***Cathy O’Neil, Weapons of Math Destruction: How Big Data Increases Inequality and Threatens Democracy [here]
*Hannah Fry, Hello World: Being Human in the Age of Algorithms [here]
***Allison K. Henrich, Emille D. Lawrence, Matthew A. Pons, and David G. Taylor, eds, Living Proof: Stories of Resilience Along the Mathematical Journey [here]

Movie Pass Math

For a month this summer, I paid $30 to get an Alamo Drafthouse Movie Pass. Alamo is a movie theater that allow serves food and drinks. What the Movie Pass allows you to do is watch a movie every day (and you only pay a $1.89 service fee). It is summer and I figured why not? I could take good advantage of this deal. I had never gone to the movies alone before, but this past month I realized I really enjoy it!

The movies I saw using the pass:

  1. Mission: Impossible – Dead Reckoning Part One
  2. The Lesson
  3. Oppenheimer
  4. Past Lives
  5. Indiana Jones and the Dial of Destiny
  6. Shortcomings
  7. Joy Ride
  8. Haunted Mansion
  9. Barbie
  10. Easy A
  11. Harry Potter and the Sorcerer’s Stone
  12. Jules

I think my favorite was just a random movie I had never heard of and went to see to pass the time — The Lesson. And I thought the best was Oppenheimer.

I wanted to see what a great deal this was for me. For the basic calculations, most movies cost between $15.50-$18.99 depending on the time of day (and all movies on Tuesdays are only $9). For simplicity’s sake, I’m going to say the total cost to me with the Movie Pass over the course of the month was going to be $30+$1.89m (where 0<m<31) for the price of the pass and the cost of the service fee per movie.

And without the movie pass, it would have been around $17m (since I saw some movies during the day, and some movies at night).

So the break-even point was seeing less than two movies! I spent a total of $52.68 with the pass to see 12 movies, while I would have spent out of pocket $204 if I didn’t have the pass and saw all 12 movies. I know money doesn’t really work like this, but in my mind I like to pretend I saved $151.32!

Another way to think about this is to calculate the price per ticket:

So at 12 movies, it was like each movie only cost me $4.39. (I was saving $12.61 per ticket!) And the more movies I would have watched, the cheaper each ticket would have been!

But of course, this isn’t totally realistic. The thing about the Alamo is that you have at your disposal when you go there delicious foods and drinks. When I got the pass, I vowed I wasn’t going to always get something to eat or drink — and it would be a rare occurrence. But… life happens and I ended up getting something to eat on 5 of the 12 times I went. And I calculated the total and it came to $91.13 in food/tips.

So in reality, I spent a total of $143.81 at the movies, and it was in total $11.98 per movie on average.

Psychologically, it’s a little bit sneaky. You think “oh, I can see so many movies for $30.” Then there’s that $1.89 fee per movie that isn’t a lot but adds up. And of course the impulse food purchases is something Alamo surely is counting on. So I can go around telling people (and myself) “I saw 12 movies for $30″… when the reality is that what I should be saying is “I saw 12 movies and spent $143.81.”

Overall, was it worth it?

Absolutely.

21st Century Mathematics Professional Development

Throughout the month of July 2023, I participated in a PD experience that was unique to me. Justin Lanier, a former math teacher turned professional mathematician, held a PD he developed called “21st Century Mathematics” and the ultimate goal was “To grow as mathematicians, both for our own enjoyment and for the benefit of our students.”

Each week in July, he provided problem sets for us to work on. Justin kindly allowed me to share these: week 1 problems, week 2 problems, and week 3 problems. Each week’s problems were related to a chapter in the book that formed the backbone of the course: Theorems of the 21st Century by Bogdan Grechuk.

This book’s author went through articles published in 2000-2010 in the prestigious Annals of Mathematics and found (at least to his opinion) the most important results, and wrote a section trying to explain to ____ precisely what that result was and if possible, the general argument used to get that result. The reason I used the blank in the previous sentence is because I am a little confused who the intended audience of the book was. What was great is that I — a math teacher who majored in math two decades ago — could follow along some of the sections. And we had a number of participants who were middle school math teachers who were playing along too.

Justin picked interesting and accessible sections of the book for us to read (one per week) and built his problem sets around those sections.

  • Week 1: Section 3.2, Representing 1 as a Sum of Reciprocals of Selected Integers.
  • Week 2: Section 2.13, Transforming Convex Bodies into Balls.
  • Week 3: Section 10.2, On Divisibility Properties of Dyson’s Rank Partition Function.

I got really hooked on the problems. They reminded me of doing super fun “morning math” at PCMI, where we got to discover new things, think in different ways, and remember the frustrations and elations of learning new math. I did hit some walls, but also had some insights I was really proud of. Since I wanted to take my hand at practicing LaTeX after many years, I typed up my work each week.

For personal archival purposes, I’m uploading my writeups for each problem set here:

21st_century_mathematics_with_justin_lanier___week_1Download
21st_century_mathematics_with_justin_lanier___week_2Download
21st_century_mathematics_with_justin_lanier___week_3Download

We had a choice of reading the section from the book the problem sets were based on before or after working on the problems. Mostly, I chose to work on the problems first, and then after finishing the problem set to the best of my ability, work on understanding the section from the book.

In addition to working on these independently, all the participants had a Discord that we were invited to to chat. I had never used Discord before, but it was pretty neat. We introduced ourselves there, and not all people used it to talk, but some of us were sharing insights and asking questions about the problems there.

Each week, we had a Zoom. Justin offered it twice each week because everyone has such different schedules in the summer. The first part of each Zoom was Justin talking to us about what it means to do research, and be a mathematician, in the 21st century. It was interesting to see some of the charts and data he collected about number of publications, number of PhDs, and gender and minority representation (or underrepresentation, as the case it, obviously). Then we broke up into breakout rooms and discussed the problem set questions.

Additionally, we were invited to read and summarize a different section in the book — whatever section felt accessible and interesting to us. I really enjoyed this part! The first week, I chose a section and then got into a long discussion of something I didn’t understand on the Discord with a few others. I honestly think I found an error in the book — not in the math, I’m sure, but in how the theorem was described in the book.

The three sections I chose to read and try to understand were:

  • Section 8.7: ”A Negative Answer to Littlewood’s Question about Zeros of Cosine Polynomials.
  • Section 10.2: ”On divisibility properties of Dyson’s rank partition function.”
  • Section 2.5: ”The Optimality of the Standard Double Bubble”

(You can read my summaries of what I understood from each section at the bottom of each problem set I turned in.)

Additionally, Justin invited mathematicians to talk to us on a Zoom each week. The truth is, this is one thing I didn’t participate in. I’m so mad at myself. I talked myself out of it, because I secretly was so nervous of being the only person in the Zoom and then having nothing to say. An irrational fear, but it won out.

Lastly, in the fourth week, Justin didn’t have problems and readings. We each were asked to create a 2-5 minute presentation on anything related to the course. Some wrote up what they learned. Others created activities for their classroom based on something they discovered mathematically or pedagogically. Some delved more into the readings. I did that.

Again, for archival purposes, here’s my presentation on “partitions” and “rank”. However just note that it’s designed for someone who read the reading.

The structure was sort of a choose-your-own adventure. You could choose to do the problems or not. You could choose to engage in the Discord or not. You could choose to the Week 4 presentation or not. I was curious how I’d feel about this being a remote PD. I’m so over Zoom that I almost didn’t sign up because of that. But it turned out that for someone like me, who wanted to do (almost) all the things, this all threaded together to make a really wonderful mathematics-filled July.

Justin didn’t charge for the course, which was great because I signed up after my school year ended so I probably couldn’t have gotten funding from my school. But in line with his values, he instead requested if we could, to donate $25 to one of these organizations.
African Institute for Mathematical Sciences (AIMS) – donate
Bridge to Enter Advanced Mathematics (BEAM) – donate
Enhancing Diversity in Graduate Education (EDGE) – donate
Julia Robinson Mathematics Festival (JRMF) – donate
Latinx and Hispanics in the Mathematical Sciences (Lathisms) – donate
Mathematically Gifted and Black (MGB) – donate

I chose two :)

I loved doing math over the summer, and having some light structure to guide me! And learn a bit about what has been happening in mathematics more recently in a different way than reading Quanta articles.

Some places of exploration for younger kids who like math and who want more joyful math play

I got an email from a college friend about their kid Sam…

Ahoy Big Sam!

I have a question regarding Lil Sam. 

He’s big on math. 

Like big big. 

Do your colleagues in the lower school / primary school have a list of resources for self-directed math exploration for the youth?

Or even applied math via games etc so its more play / exploration vs workbooks?

It got to the point that he was asking us to come up with math questions that we just bought a stack of workbooks but those feel like work and less development of interest and joy. 

Now I don’t know anything about little kids. But I love that my friend wasn’t looking for workbooks and was more interested in “joy” and “play.” Below are what I’m going to recommend to my friend, but I think would be a useful list for any kid in pre-Kindergarten to grade 5.

Beast Academy: I remember another college friend reached out years ago with a similar question, and I turned to the online math teacher community and pretty universally I got “Beast Academy” as an answer over and over again.

I reached out to a kindergarten teacher who I adore (I mean, she plays board games with me). I once told her how much I was loving Tracy Zager’s book Becoming the Math Teacher You Wish You’d Had even though it was written for elementary school teachers, and she picked it up and read it! So she’s quality people. I also reached out to our lower school math coach. Both said the same thing:

Tang Math: especially the summer challenges.

Then I reached out to my new math teacher community on Mathstodon, and got additional suggestions:

MathPickle: I went to this site and loved it, and there is a link to a super fun activity book called the “Infinite Pickle” and upon quick browsing, I’m excited by it! And tons of puzzles! There’s also a page with lots of suggested board games and at the top of that page, it reads “#1 job for parents: establish a culture of board gaming in the home.” You know I’m a fan of board games, so I’m into all of this.

DragonBox Numbers game: not only did I hear about this online, but I went to a Desmos Fellows Conference a couple weeks ago and a few elementary school teachers were raving about this over lunch one day. So I heard about this twice in a few weeks when I had never heard about it before! Also, one can learn chess, apparently, with DragonBox chess and that was recommeded too.

Math For Love, of course! I’ve known about this site for years, with all the rich tasks and games (like Tiny Polka Dot!). There are lesson openers, rich tasks, and games (all sortable by grade level!).

Yokaku puzzles were recommended and were a new type of puzzle to me, and I think these are designed to build number sense and fluency — and can be written from the youngest students to the oldest students (like I saw some things I could use in my high school classes!).

Math Games with Bad Drawings is an awesome book by Ben Orlin (which might have my name in it, in a very tiny endnote) which is chock full of games (most new) that involve very little other than pencil and paper and maybe an occasional coin or paperclip) that I absolutely know I would use with my own children if I had any. Plus I think my friend who asked for suggestions would love reading the book (the prose is humorous) to get the games to teach his kids.

The easier levels of Area Mazes and Strimko puzzles were also thrown out there. I hadn’t heard of these types of puzzles, but when I googled, of course the great Sarah Carter comes to the rescue with really informative pages both on Area Mazes and Strimko puzzles.

Lastly, as I was putting together this post, I remembered two more resources that might be helpful to my friend. Kent Haines’ website Games for Young Minds and Christopher Danielson’s Talking Math With Your Kids. Both are deliciously wonderful. I definitely have bought the books “How Many?” and “Which One Doesn’t Belong” along with many fun play tiles from Christopher Danielson’s shop and highly recommend them.

I figure this post can be my personal repository if anyone asks for fun math enrichment on the pre-K to 5 level. But PLEASE leave a comment if you have any additional suggestions! I’m always looking for things to expand my knolwedge of cool math resources.

UPDATE: Ahhhh, I can’t believe I forgot this. At the Desmos Fellows Conference, the TV show on netflix Numberblocks came up a few times! And there’s a youtube channel. I even watched a few episodes with my niece and nephew and I really enjoyed them. (I think they were less excited about it because they’re older and we started with the very first episode.)

UPDATE 2: My friend who works for Illustrative Math said their “IM math centers” could be useful too! She expanded: “Go to link, navigate to a grade, find the tab that says “Centers” and poke around. I’ve heard they can be a bit hard to navigate at first just because there are a lot of them, and each one has ‘stages’ of increasing complexity. But if you download any set of blackline masters, the directions are written on them in kid-friendly language. Primary teachers sometimes mean different things by ‘centers’ but I take it to mean an activity that kids can do without adult supervision to practice or work on number sense.”

PCMI Post 5: Ketchup Math

Today I was sitting at a lunch table of 8 people. We somehow got on the topic of grilled cheese. You may know that I’m a vegetarian, but I think a more accurate term for me is a queso-carbotarian because I love cheese and carbs together. So I’m a real fan of grilled cheese. And growing up, when my mom made me grilled cheese made with American singles inbetween two pieces of white bread, she always served it with ketchup.

I thought that was normal. That everyone ate their grilled cheese with ketchup. I mean, yes, you can dip it in tomato soup. And you can dip it in ketchup. And maybe, just maybe, you could eat it by itself. And everyone is going to have their own opinions about what’s best.

What I wasn’t prepared for is that no one at my table of 8 had ever even heard of eating grilled cheese by dipping it in ketchup. I’m not talking about not liking it, or not doing it. They hadn’t ever heard of anyone doing it.

While I was totally certain that everyone at least must have heard of it, and I’d have guessed that most people did it except for just a few. So that fact that of the 8 of us, I was the only one who heard of it led me to believe one of two things:

I was at a very weird table that was not representative of the rest of the American/Canadian population, or that I grew up with this very unique cultural tradition of eating grilled cheese with ketchup — and that was something my mom invented or maybe it’s an Indian thing — but not widely known.

Of course I decided to double down, and claim that my lunch table was TOTALLY WEIRD and that they were the outlier — and more people had to have heard of ketchup and grilled cheese. So I get up to ask another group of around 6 teachers at a neighboring table. And what happened? They all said the combination was new to them. (And later in the day, I ran into author and mathematician Jordan Ellenberg who also said he had never heard of the combination, but understood why it would likely be good.)

Now at this point I feel like my world is crashing down. Something that I thought was so commonplace in the world wasn’t. My sense of reality was being called into question. And instead of accepting it, I double down again. Everyone at my table is interested in this — maybe because I feel totally bonkers and can’t let it go. So I put up a poll on twitter, set for 3 hours, which asks the question below and gets these results from 41 people:

Another person at the table did a similar poll on facebook, and got 25-ish results, and they said about 2/3rds of the respondants said “yes.”

What to conclude?

I figure I can think of it like this. I want to know if my two lunch tables of 14 people (where 13 hadn’t heard of eating grilled cheese with ketchup) WEIRD or if I am WEIRD for doing this. I am using the two polls to be representative of the true population… and to make things easier, I’d even argue there’s some error and so maybe I could even say about 50% of the world has heard of eating grilled cheese with ketchup, and 50% of the world hasn’t heard of eating grilled cheese with ketchup.

Then in a group of 14, for only 1 person to have heard of eating grilled cheese with ketchup IS TOTALLY WEIRD. It’s like flipping a coin 14 times, and only one time you get heads (and 13 times you get tails). Hello binomial distribution.

SO MY TABLES WERE WEIRD.

But… I still don’t know… tonight we had an event at 7pm where a bunch of people showed up. Maybe there were 20 people in the room and the ketchup question was asked and I think only 3 or 4 people had heard of eating grilled cheese with ketchup. So I’m not sure what’s up.

Regardless, I loved this random fun math question that popped up as I was having a mental breakdown involving the internal reality of my world. And that others got into it.

P.S. For another fun condiment digression, our lunch table then started talking about the tiktok trend where people put yellow mustard on oreos and claimed it was so so good. Even Lizzo tried it. Randomly, there was a box of oreos on a table in our classroom, and we had mustard packets from lunch . So later in the day, another person and I tried the combination. I have a screenshot of the video someone took where I tried it. It wasn’t awful at all, but it wasn’t like enhancing the flavor either for me. It was just kinda fine.