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Justin Lanier

@jlanier.bsky.social
206 followers 102 following 138 posts
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Reposted by Justin Lanier
Nalini Joshi @monsoon0.bsky.social · 13/08/2026
Terry Tao’s @teorth.bsky.social ‘s public lecture “Mathematics In the Age of AI” #ICM2026 is now available to watch online: www.simonsfoundation.org/2026/08/13/f...
simonsfoundation.org
Watch: Fields Medalist Terence Tao on Artificial Intelligence and Why We Do Math
Watch: Fields Medalist Terence Tao on Artificial Intelligence and Why We Do Math on Simons Foundation
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Reposted by Justin Lanier
Michael Pershan @mpershan.bsky.social · 07/07/2026
I wrote about how @hpicciotto.bsky.social makes such wonderful (and useful) mathematical activities. substack.com/home/post/p-...
substack.com
How Henri Picciotto Designs Great Lessons
Learning from one of the best to ever do it.
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Reposted by Justin Lanier
Fawn Nguyen @fawnnguyen.substack.com · 05/07/2026
Last week in Phoenix, a teacher filled in "school math is ___" with one word: required. New post about this deadpan truth. fawnnguyen.substack.com/p/the-anti-s...
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Reposted by Justin Lanier
Justin Lanier @jlanier.bsky.social · 22/06/2026
What do mathematicians do? How do they make new mathematical discoveries? Why does that matter for K-12 math education? If you are a math teacher and you are curious about these questions, join in on "21st century mathematics" in July! Free, online, and flexible. www.youtube.com/watch?v=5UIx...
youtube.com
"21st century mathematics" returns in July 2026!
YouTube video by Justin Lanier
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Justin Lanier @jlanier.bsky.social · 22/06/2026
What do mathematicians do? How do they make new mathematical discoveries? Why does that matter for K-12 math education? If you are a math teacher and you are curious about these questions, join in on "21st century mathematics" in July! Free, online, and flexible. www.youtube.com/watch?v=5UIx...
youtube.com
"21st century mathematics" returns in July 2026!
YouTube video by Justin Lanier
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Reposted by Justin Lanier
Justin Lanier @jlanier.bsky.social · 19/06/2026
Hi! In July I'm once again running a free online program for K-12 math teachers called "21st century mathematics". Its goal is to help teachers to connect math they teach with some math that has been discovered in the 21st century. Pass it along! Info+register: justinlanier.org/21st-century...
A 4x4 puzzle grid, indicating an example of an alternating sign matrix; an example of a configuration of 21 points that maximized the number of pairs that are a unit distance apart. These are the two mathematical themes of the 2026 program.
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Justin Lanier @jlanier.bsky.social · 19/06/2026
Hi! In July I'm once again running a free online program for K-12 math teachers called "21st century mathematics". Its goal is to help teachers to connect math they teach with some math that has been discovered in the 21st century. Pass it along! Info+register: justinlanier.org/21st-century...
A 4x4 puzzle grid, indicating an example of an alternating sign matrix; an example of a configuration of 21 points that maximized the number of pairs that are a unit distance apart. These are the two mathematical themes of the 2026 program.
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Justin Lanier @jlanier.bsky.social · 03/06/2026
@nhoskee.bsky.social @triangleman.bsky.social Hi! I haven't run across any Summer of Math announcements for this summer. Any updates for this or future summers at this time? Thanks!
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Reposted by Justin Lanier
Christopher Danielson @triangleman.bsky.social · 19/02/2026
We were invited to read from our books, which I did of course. But first I had some opening words, which I thought I'd share with you here. I'll share video too, once that's available.
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Justin Lanier @jlanier.bsky.social · 11/02/2026
TIL that Fibonacci dedicated his famous book “Liber Abaci” to one Michael Scott. 😂
media.tenor.com
a man in a suit and tie is making a funny face
Alt: “The Office” character Michael Scott in a suit and tie looking surprised and happy.
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Justin Lanier @jlanier.bsky.social · 25/01/2026
@jonbois.bsky.social watching football
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Reposted by Justin Lanier
Christopher Danielson @triangleman.bsky.social · 03/11/2025
Really nice piece on math and democracy here. (gift link) www.nytimes.com/2025/11/03/s...
nytimes.com
Moon Duchin on the ‘Mathematical Quagmire’ of Gerrymandering
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Justin Lanier @jlanier.bsky.social · 02/11/2025
If you teach Year 6 maths in the UK and you'd be willing to Zoom chat briefly with a pre-service teacher in the US for a class project, let me know? Thanks!
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Reposted by Justin Lanier
benjamin dickman @benjamindickman.bsky.social · 09/08/2025
I presented on this problem today! You can find the slides here: docs.google.com/presentation... I don't use speaker notes (just vibes) but I think a recorded version exists and I'll try to link to it if/when I can. cc #iTeachMath ♾️ bcc #MathSky 🧮
docs.google.com
21st Century Math [2025] Explorations from Fibonacci Nim
Explorations from Fibonacci Nim Ideas, Wonders, and Unresolved Problems Inspired by the 21st Century Mathematics 2025 Program Benjamin Dickman, Ph.D. || K-12 Mathematics Chair & Teacher Department of ...
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Reposted by Justin Lanier
Rob Eastaway @robeastaway.bsky.social · 31/07/2025
Yesterday I spent a fascinating morning talking maths with a group of GPs. All professions require some level of numeracy, but doctors face particular challenges when communicating mathematical ideas. I've written up a short blog: robeastaway.com/blog/gp-maths
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Reposted by Justin Lanier
Sydney Mathematical Research Institute (SMRI) @sydmathinst.bsky.social · 03/07/2025
Applications are now open for our International Visitor Program, open to #mathematicians to visit Aus 🐨 between July '26-'June 27, or March '26-June -27 (Aus/NZ citizens) 📅 Apply by Aug 1, info: mathematical-research-institute.sydney.edu.au/internationa... Please share with your networks 🔁 #MathSky
mathematical-research-institute.sydney.edu.au
International Visitor Program - Sydney Mathematical Research Institute
IVP August 2023 applications are due 8 August 2023, for July 2024–June 2025 visits (general applicants) & March 2024–June 2025 for Australian citizens/PR & NZ citizens.
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Reposted by Justin Lanier
Justin Lanier @jlanier.bsky.social · 23/04/2025
“21st century mathematics”: a free month-long online enrichment program for math teachers. Info + register: bit.ly/21math2025 Video part 1:
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Justin Lanier @jlanier.bsky.social · 27/06/2025
TIL that we narrowly missing lugging around not only the monikers "imaginary", "negative", "complex", and "irrational" for numbers, but also "fictitious limits". Real glad for that. 😅 from MacTutor's "The real numbers: Stevin to Hilbert"
Two years after the publication of Hankel's monograph, Méray published "Remarques sur la nature des quantités" in which he considered Cauchy sequences of rational numbers which, if they did not converge to a rational limit, had what he called a "fictitious limit". He then considered the real numbers to consist of the rational numbers and his fictitious limits.
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Justin Lanier @jlanier.bsky.social · 23/06/2025
We are two weeks out from the start of "21st century mathematics", a program I run for K-12 math teachers. (Register now!) The program helps teachers connect the math they teach with some math that has been discovered in the 21st century. The program is flexible, free, & online.
A picture of a double bubble. A picture of the first 18 Fibonacci numbers, with the ones that are perfect powers highlighted.
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Reposted by Justin Lanier
NCTM @nctm.org · 05/06/2025
"While everyone is glad to have a much-deserved break from the routine of early mornings and late evenings, as teachers we often end the school year thinking about the things we 'just didn’t have time to cover'." Read NCTM President @latrendak.bsky.social's full message here: nctm.link/a3H7t
President's Message: What Are Your Summer Math Plans? Headshot of Latrenda Knighten
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Reposted by Justin Lanier
Christopher Danielson @triangleman.bsky.social · 30/05/2025
Have you followed along with Math On-A-Stick and wondered what it would take to make this kind of joyful, creative math happen in your locality? Well, let's gooooooooooooooo www.mathhappens.org/math-at-the-...
mathhappens.org
Math at the Fair - MathHappens
Math at the Fair MathHappens Foundation is inviting applications for teams to participate in Math at the Fair, a project that aims to build playful and creative math experiences at fairs and similar e...
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Justin Lanier @jlanier.bsky.social · 06/05/2025
www.nytimes.com/2025/05/05/u...
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Justin Lanier @jlanier.bsky.social · 03/05/2025
Big day here in Australia.
Google suggested search results for "democra":
democracy
democracy sausage
democracy sausage map
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Reposted by Justin Lanier
Justin Lanier @jlanier.bsky.social · 28/04/2025
Ten squares. The first example has perimeter 14. The second one has perimeter 22. Can anyone find ones with smaller or bigger perimeters? Or other examples that match these? Intrigued? Check out "21st century mathematics", an enrichment program for teachers: justinlanier.org/21st-century...
Ten squares arranged in two different ways: a 2x3 rectangle with a 2x2 square stuck to its side, and one that goes like this:
00X00
0XXX0
XX0XX
X000X

where the X's are the squares and the 0'x are empty space.
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Justin Lanier @jlanier.bsky.social · 28/04/2025
Ten squares. The first example has perimeter 14. The second one has perimeter 22. Can anyone find ones with smaller or bigger perimeters? Or other examples that match these? Intrigued? Check out "21st century mathematics", an enrichment program for teachers: justinlanier.org/21st-century...
Ten squares arranged in two different ways: a 2x3 rectangle with a 2x2 square stuck to its side, and one that goes like this:
00X00
0XXX0
XX0XX
X000X

where the X's are the squares and the 0'x are empty space.
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Reposted by Justin Lanier
Nalini Joshi @monsoon0.bsky.social · 23/04/2025
Are you a mathematics teacher? Would you like a taste of 21st century mathematics? See the link below to join a program for teachers run by Justin Lanier @jlanier.bsky.social —stay for as long as you like, explore with friends, & get your own insights into accessible, deep questions in math
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Justin Lanier @jlanier.bsky.social · 23/04/2025
“21st century mathematics”: a free month-long online enrichment program for math teachers. Info + register: bit.ly/21math2025 Video part 1:
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Reposted by Justin Lanier
Justin Lanier @jlanier.bsky.social · 16/04/2025
Hi! In July I'm once again running a program for K-12 math teachers called "21st century mathematics". Its goal is to help teachers to connect math they teach with some math that has been discovered in the 21st century. Pass it along! Info+register: justinlanier.org/21st-century...
justinlanier.org
21st century mathematics – 2025
An online learning experience for math teachers Registration for the 2025 program is now open! Here is the registration form. Registration will continue through the start of the program in July. Al…
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Justin Lanier @jlanier.bsky.social · 16/04/2025
Hi! In July I'm once again running a program for K-12 math teachers called "21st century mathematics". Its goal is to help teachers to connect math they teach with some math that has been discovered in the 21st century. Pass it along! Info+register: justinlanier.org/21st-century...
justinlanier.org
21st century mathematics – 2025
An online learning experience for math teachers Registration for the 2025 program is now open! Here is the registration form. Registration will continue through the start of the program in July. Al…
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Justin Lanier @jlanier.bsky.social · 01/04/2025
"𝘉𝘳𝘪𝘯𝘨 𝘐𝘵 𝘖𝘯: 𝘐𝘯 𝘐𝘵 𝘵𝘰 𝘞𝘪𝘯 and 𝘞𝘦𝘴𝘵 𝘚𝘪𝘥𝘦 𝘚𝘵𝘰𝘳𝘺 are basically the same movie. They're romeomorphic."
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Justin Lanier @jlanier.bsky.social · 06/03/2025
Find the derivative of f(x) = sin²(x) + cos²(x) in two different ways.
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Reposted by Justin Lanier
Dr. Courtney Gibbons (she/her/xlookup) @courtneygibbons.phd · 01/02/2025
Here's the first page of Radical Equations; I hope it grabs your attention! It's available from lots of independent booksellers, and it's available digitally via Kindle and Audible. (Ask your library to get a copy!)
CHAPTER 1
Algebra and Civil Rights?

[start of inset quotation] 
In order for us as poor and oppressed people to become a part of a society that is meaningful, the system under which we now exist has to be radically changed. This means that we are going to have to learn to think in radical terms. I use the term radical in its original meaning-getting down to and understanding the root cause. It means facing a system that does not lend itself to your needs and devising means by which you change that system. That is easier said than done. But one of the things that has to be faced is, in the process of wanting to change that system, how much have we got to do to find out who we are, where we have come from and where we are going.... I am saying as you must say, too, that in order to see where we are going, we not only must remember where we have been, but we must understand where we have been.
–Ella Baker
[end of inset quotation]

The sit-ins woke me up.
Until then, my Black life was conflicted. I was a twenty-six-year-old teacher at Horace Mann, an elite private school in the Bronx, moving back and forth between the sharply contrasting worlds of Hamilton College, Harvard University, Horace Mann, and Harlem.

[the first page of Radical Equations]
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Justin Lanier @jlanier.bsky.social · 31/01/2025
Advice please: Someone registers for a program I run (through a Google Form) & gives me their email address. But when I try emailing them later, maybe it gets sent to their spam, or maybe they mistyped and I receive an error message back. What's a good way to automate an email confirmation check?
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Reposted by Justin Lanier
Dylan Kane @dylanpkane.bsky.social · 21/01/2025
Reflecting on explorations in math place, and something called the Rosenthal Prize: fivetwelvethirteen.substack.com/p/exploratio...
fivetwelvethirteen.substack.com
Explorations in Math Class
Quality over quantity
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Reposted by Justin Lanier
Avery @averypickford.bsky.social · 16/01/2025
Alright, help me fill up this starter pack. Are there other current K-12 classroom teachers who want to be added, or have cutbacks reduced the math teaching community to this list of 64 (wonderful) individuals? 😂
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Justin Lanier @jlanier.bsky.social · 31/12/2024
Who are you cheering for tonight? - 2024 - 2025 - I just hope it's a good game.
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Justin Lanier @jlanier.bsky.social · 10/10/2024
If you enjoyed this median-mode-range prompt, check out this "averages inquiry" that I ran across, over on Inquiry Maths. Lots of great stuff! www.inquirymaths.com/home/statist...
inquirymaths.com
Inquiry Maths - Averages
The prompt
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Justin Lanier @jlanier.bsky.social · 04/10/2024
Let's have some numbers so that their median is 4, their mode is 2, and their range is 10. What are some possibilities? And then: what could the mean of such a collection of numbers be? What *couldn't* their mean be?
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