信言不美，美言不信。

I get a lot of questions that are so general that there is no useful answer I can give, e.g., “how do I get better at geometry?”. What do you want from me? Go do more problems, sheesh.

These days, in my instructions for contacting me, I tell people to be as specific as possible e.g. including specific problems they recently tried and couldn’t solve. Unsurpisingly the same kind of people who ask me a question like that are also not the kind of people who read instructions, so it hasn’t helped much. 😛

But it’s occurred to me it’s possible to take this too far. Or maybe more accurately, it’s always better to ask a specific question, but sometimes the best answer will still be “go do more problems, sheesh”.

Here’s a metaphorical example …

I went and took the idea in I switched to point-based problem sets one step further this year. Now the OTIS-WEB page looks like this:

Makes it feel a bit more rewarding to complete problem sets, I think. Also gives me the chance to plant Easter eggs everywhere, which is always a lot of fun ;)

If you want to see how this is done, the source is up on GitHub.

This is a pitch for a new text that I’m thinking of writing. I want to post it here to solicit opinions from the general community before investing a lot of time into the actual writing.

Summary

There are a lot of students who ask me a question isomorphic to:

How do I learn to write proofs?

I’ve got this on my Q&A. For the contest kiddos out there, it basically amounts to saying “read the official solutions to any competition”.

But I think I can do better.

Requirements

Calling into question the obvious, by insisting that it be “rigorously proved”, is to say to a student, “Your feelings and ideas are suspect. You need to think and speak our way.”

Now there is a place for formal proof in mathematics, no question. But that place is not a student’s first introduction to mathematical argument. At …

I might be going too far with this Arch Linux brand loyalty, but I am so psyched I don’t care.

There’s three pieces of hardware that I’ve always kind of wanted but never been willing to spend money on in isolation:

• A handheld gaming console
• A laptop with a touch screen
• A laptop with enough power to play games on a Steam library (my laptop is a bit too old for this)

So when I heard the Steam Deck existed and it would be running an Arch Linux system beneath it, I totally caved.

I’m just sad I didn’t hear about in time to be early enough in the queue to get it by Christmas. Ah well.

In unrelated news, careful readers might notice that the blog has been moved to blog.evanchen.cc. I think the old URL usamo.wordpress.com will continue to …

Sometime this week the American Math Competitions released the following new policy:

For the IMO, EGMO, RMM, TSTSTs, and TSTs, and MOP, students must be US citizens or US permanent residents. Visas are not a valid substitute. (AMC Policies)

I want to make a rather brief statement on why I was opposed to this change. To do this I want to draw an analogy. In the American Math Competitions, students are asked what gender they identify with, which is used to determine whether they are eligible for the European Girl’s Math Olympiad and also for invitations to MOP.

This means that in theory, you could try to abuse the system by deliberately misrepresenting your self-identified gender. But in practice, nobody has attempted this. So, we continue to allow students to self-identify their gender, in order to make sure to be inclusive to students with gender dysphoria, and trusting our …

I worked with a few friends on writing a mini one-round puzzle hunt for this year’s MOP students. If you want to play, you can do so now at the following URL:

https://mosp.evanchen.cc

I’m not sure whether or not this is going to become a recurring tradition. On the one hand, it was loads of fun to make (including figuring out how to draw art on my iPad); on the other hand, I definitely didn’t blow a couple hundred hours of my life putting this together. ;)

Unrelated advertisement: the Carina Initiatives is currently looking to hire a junior data scientist. They’re a young philanthropic fund that’s interested in supporting initiatives that build actual math problem solving (like, the problem-solving you’d see on this blog, not the mainstream buzzword stuff). I’ve had a lot of fun talking with them over the …

As a follow-up to the previous post, I am recording here some details about the (numerous, varied, and deep) revisions that a bunch of my puzzles went through during the production process. These puzzles are in chronological order of when I wrote the puzzle.

Spoiler warning: Unlike the last post, these will completely spoil all of the puzzles below.

1. A Bit of Light

Surprisingly, the gist of the puzzle mostly survived revisions: the idea of an encoding-based puzzle with the key step to look at seven-segment displays between the Braille and resistor color encoding. One issue I ran into while constructing was that ABCDEF6 is actually too big in base 16 to store in an eight-bit number, which is part of why I ended up 1337-ing the seven-segment display bits.

The 2021 Mystery Hunt concluded a while ago, and wow, what an experience. I was lucky enough to be on the organizing team, and I am so proud right now to be able to say I am a ✈️✈️✈️ Galactic Trensdetter ✈️✈️✈️. (If you don’t know what a puzzle hunt is, betaveros has a great introduction.)

I came in to the MIT Mystery Hunt with no writing experience at all, and ended up being listed as the author of a few. It was a trial by fire, to say the least.

In this post I want to say a bit about the parts of the puzzle-writing process that surprised me the most, in the hopes that maybe it would be helpful to future authors. A nice introduction is given by e.g. David Wilson, which I read many times before I actually attempted to write my first puzzle. Most of what …

In this post I’m hoping to say a bit about the process that’s used for the problem selection of the recent USEMO: how one goes from a pool of problem proposals to a six-problem test. (How to write problems is an entirely different story, and deserves its own post.) I choose USEMO for concreteness here, but I imagine a similar procedure could be used for many other contests.

I hope this might be of interest to students preparing for contests to see a bit of the behind-the-scenes, and maybe helpful for other organizers of olympiads.

The overview of the entire timeline is:

1. Submission period for authors (5-10 weeks)
2. Creating the packet
3. Reviewing period where volunteers try out the proposed problems (6-12 weeks)
4. Editing and deciding on a draft of the test
5. Test-solving of the draft of the test (3-5 weeks)
6. Finalizing and wrap-up

Now I’ll talk about …

A lot of people have been asking me how team selection is going to work for the USA this year. This information was sent out to the contestants a while ago, but I understand that there’s a lot of people outside of MOP 2020 who are interested in seeing the TST problems :) so this is a quick overview of how things are going down this year.

This year there are six tests leading to the IMO 2021 team:

• USA TSTST Day 1: November 12, 2020 (3 problems, 4.5 hours)
• USA TSTST Day 2: December 10, 2020 (3 problems, 4.5 hours)
• USA TSTST Day 3: January 21, 2021 (3 problems, 4.5 hours)
• RMM Day 1: February 2021 (3 problems, 4.5 hours)
• APMO: March 2021 (5 problems, 4 hours)
• USAMO: April 2021 (2 days, each with 3 problems and 4.5 hours)

Everyone who was at the …