Circular optimization

This post will mostly be focused on construction-type problems in which you're asked to construct something satisfying property $latex {P}&fg=000000$. Minor spoilers for USAMO 2011/4, IMO 2014/5. 1. What is a leap of faith? Usually, a good thing to do whenever you can is to make ``safe moves'' which are implied by the property $latex… Continue reading Circular optimization

Meritocracy is the worst form of admissions except for all the other ones

I'm now going to say something explicitly that I hinted at in June: I don't think a student deserves to make MOP more because they had a higher score than another student. I think it's easy to get this impression because the selection for MOP is done by score cutoffs. So it sure looks that… Continue reading Meritocracy is the worst form of admissions except for all the other ones

MOHS hardness scale

There's a new addition to my olympiad problems and solutions archive: I created an index of many past IMO/USAMO/USA TST(ST) problems by what my opinions on their difficulties are. You can grab the direct link to the file below: https://evanchen.cc/upload/MOHS-hardness.pdf In short, the scale runs from 0M to 50M in increments of 5M, and every… Continue reading MOHS hardness scale

Understanding with System 1

Math must be presented for System 1 to absorb and only incidentally for System 2 to verify. I finally have a sort-of formalizable guideline for teaching and writing math, and what it means to "understand" math. I've been unconsciously following this for years and only now managed to write down explicitly what it is that… Continue reading Understanding with System 1

MOP should do a better job of supporting its students in not-June

Up to now I always felt a little saddened when I see people drop out of the IMO or EGMO team selection. But actually, really I should be asking myself what I (as a coach) could do better to make sure the students know we value their effort, even if they ultimately don't make the… Continue reading MOP should do a better job of supporting its students in not-June

IMO 2019 Aftermath

Here is my commentary for the 2019 International Math Olympiad, consisting of pictures and some political statements about the problem. Summary This year's USA delegation consisted of leader Po-Shen Loh and deputy leader Yang Liu. The USA scored 227 points, tying for first place with China. For context, that is missing a total of four… Continue reading IMO 2019 Aftermath

Hard and soft techniques

In yet another contest-based post, I want to distinguish between two types of thinking: things that could help you solve a problem, and things that could help you understand the problem better. Then I'll talk a little about how you can use the latter. (I've talked about this in my own classes for a while… Continue reading Hard and soft techniques

Undergraduate Math 011: a firsT yeaR coursE in geometrY

tl;dr I parodied my own book, download the new version here. People often complain to me about how olympiad geometry is just about knowing a bunch of configurations or theorems. But it recently occurred to me that when you actually get down to its core, the amount of specific knowledge that you need to do… Continue reading Undergraduate Math 011: a firsT yeaR coursE in geometrY

RMM 2019 pictures and aftermath

Pictures, thoughts, and other festives from the 2019 Romania Masters in Math. See also the MAA press release. Summary Po-Shen Loh and I spent the last week in Bucharest with the United States team for the 11th RMM. The USA usually sends four students who have not attended a previous IMO or RMM before. This… Continue reading RMM 2019 pictures and aftermath