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k a March Highlights and 2025 AoPS Online Class Information
jlacosta   0
Mar 2, 2025
March is the month for State MATHCOUNTS competitions! Kudos to everyone who participated in their local chapter competitions and best of luck to all going to State! Join us on March 11th for a Math Jam devoted to our favorite Chapter competition problems! Are you interested in training for MATHCOUNTS? Be sure to check out our AMC 8/MATHCOUNTS Basics and Advanced courses.

Are you ready to level up with Olympiad training? Registration is open with early bird pricing available for our WOOT programs: MathWOOT (Levels 1 and 2), CodeWOOT, PhysicsWOOT, and ChemWOOT. What is WOOT? WOOT stands for Worldwide Online Olympiad Training and is a 7-month high school math Olympiad preparation and testing program that brings together many of the best students from around the world to learn Olympiad problem solving skills. Classes begin in September!

Do you have plans this summer? There are so many options to fit your schedule and goals whether attending a summer camp or taking online classes, it can be a great break from the routine of the school year. Check out our summer courses at AoPS Online, or if you want a math or language arts class that doesn’t have homework, but is an enriching summer experience, our AoPS Virtual Campus summer camps may be just the ticket! We are expanding our locations for our AoPS Academies across the country with 15 locations so far and new campuses opening in Saratoga CA, Johns Creek GA, and the Upper West Side NY. Check out this page for summer camp information.

Be sure to mark your calendars for the following events:
[list][*]March 5th (Wednesday), 4:30pm PT/7:30pm ET, HCSSiM Math Jam 2025. Amber Verser, Assistant Director of the Hampshire College Summer Studies in Mathematics, will host an information session about HCSSiM, a summer program for high school students.
[*]March 6th (Thursday), 4:00pm PT/7:00pm ET, Free Webinar on Math Competitions from elementary through high school. Join us for an enlightening session that demystifies the world of math competitions and helps you make informed decisions about your contest journey.
[*]March 11th (Tuesday), 4:30pm PT/7:30pm ET, 2025 MATHCOUNTS Chapter Discussion MATH JAM. AoPS instructors will discuss some of their favorite problems from the MATHCOUNTS Chapter Competition. All are welcome!
[*]March 13th (Thursday), 4:00pm PT/7:00pm ET, Free Webinar about Summer Camps at the Virtual Campus. Transform your summer into an unforgettable learning adventure! From elementary through high school, we offer dynamic summer camps featuring topics in mathematics, language arts, and competition preparation - all designed to fit your schedule and ignite your passion for learning.[/list]
Our full course list for upcoming classes is below:
All classes run 7:30pm-8:45pm ET/4:30pm - 5:45pm PT unless otherwise noted.

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0 replies
jlacosta
Mar 2, 2025
0 replies
k i Peer-to-Peer Programs Forum
jwelsh   157
N Dec 11, 2023 by cw357
Many of our AoPS Community members share their knowledge with their peers in a variety of ways, ranging from creating mock contests to creating real contests to writing handouts to hosting sessions as part of our partnership with schoolhouse.world.

To facilitate students in these efforts, we have created a new Peer-to-Peer Programs forum. With the creation of this forum, we are starting a new process for those of you who want to advertise your efforts. These advertisements and ensuing discussions have been cluttering up some of the forums that were meant for other purposes, so we’re gathering these topics in one place. This also allows students to find new peer-to-peer learning opportunities without having to poke around all the other forums.

To announce your program, or to invite others to work with you on it, here’s what to do:

1) Post a new topic in the Peer-to-Peer Programs forum. This will be the discussion thread for your program.

2) Post a single brief post in this thread that links the discussion thread of your program in the Peer-to-Peer Programs forum.

Please note that we’ll move or delete any future advertisement posts that are outside the Peer-to-Peer Programs forum, as well as any posts in this topic that are not brief announcements of new opportunities. In particular, this topic should not be used to discuss specific programs; those discussions should occur in topics in the Peer-to-Peer Programs forum.

Your post in this thread should have what you're sharing (class, session, tutoring, handout, math or coding game/other program) and a link to the thread in the Peer-to-Peer Programs forum, which should have more information (like where to find what you're sharing).
157 replies
jwelsh
Mar 15, 2021
cw357
Dec 11, 2023
k i C&P posting recs by mods
v_Enhance   0
Jun 12, 2020
The purpose of this post is to lay out a few suggestions about what kind of posts work well for the C&P forum. Except in a few cases these are mostly meant to be "suggestions based on historical trends" rather than firm hard rules; we may eventually replace this with an actual list of firm rules but that requires admin approval :) That said, if you post something in the "discouraged" category, you should not be totally surprised if it gets locked; they are discouraged exactly because past experience shows they tend to go badly.
-----------------------------
1. Program discussion: Allowed
If you have questions about specific camps or programs (e.g. which classes are good at X camp?), these questions fit well here. Many camps/programs have specific sub-forums too but we understand a lot of them are not active.
-----------------------------
2. Results discussion: Allowed
You can make threads about e.g. how you did on contests (including AMC), though on AMC day when there is a lot of discussion. Moderators and administrators may do a lot of thread-merging / forum-wrangling to keep things in one place.
-----------------------------
3. Reposting solutions or questions to past AMC/AIME/USAMO problems: Allowed
This forum contains a post for nearly every problem from AMC8, AMC10, AMC12, AIME, USAJMO, USAMO (and these links give you an index of all these posts). It is always permitted to post a full solution to any problem in its own thread (linked above), regardless of how old the problem is, and even if this solution is similar to one that has already been posted. We encourage this type of posting because it is helpful for the user to explain their solution in full to an audience, and for future users who want to see multiple approaches to a problem or even just the frequency distribution of common approaches. We do ask for some explanation; if you just post "the answer is (B); ez" then you are not adding anything useful.

You are also encouraged to post questions about a specific problem in the specific thread for that problem, or about previous user's solutions. It's almost always better to use the existing thread than to start a new one, to keep all the discussion in one place easily searchable for future visitors.
-----------------------------
4. Advice posts: Allowed, but read below first
You can use this forum to ask for advice about how to prepare for math competitions in general. But you should be aware that this question has been asked many many times. Before making a post, you are encouraged to look at the following:
[list]
[*] Stop looking for the right training: A generic post about advice that keeps getting stickied :)
[*] There is an enormous list of links on the Wiki of books / problems / etc for all levels.
[/list]
When you do post, we really encourage you to be as specific as possible in your question. Tell us about your background, what you've tried already, etc.

Actually, the absolute best way to get a helpful response is to take a few examples of problems that you tried to solve but couldn't, and explain what you tried on them / why you couldn't solve them. Here is a great example of a specific question.
-----------------------------
5. Publicity: use P2P forum instead
See https://artofproblemsolving.com/community/c5h2489297_peertopeer_programs_forum.
Some exceptions have been allowed in the past, but these require approval from administrators. (I am not totally sure what the criteria is. I am not an administrator.)
-----------------------------
6. Mock contests: use Mock Contests forum instead
Mock contests should be posted in the dedicated forum instead:
https://artofproblemsolving.com/community/c594864_aops_mock_contests
-----------------------------
7. AMC procedural questions: suggest to contact the AMC HQ instead
If you have a question like "how do I submit a change of venue form for the AIME" or "why is my name not on the qualifiers list even though I have a 300 index", you would be better off calling or emailing the AMC program to ask, they are the ones who can help you :)
-----------------------------
8. Discussion of random math problems: suggest to use MSM/HSM/HSO instead
If you are discussing a specific math problem that isn't from the AMC/AIME/USAMO, it's better to post these in Middle School Math, High School Math, High School Olympiads instead.
-----------------------------
9. Politics: suggest to use Round Table instead
There are important conversations to be had about things like gender diversity in math contests, etc., for sure. However, from experience we think that C&P is historically not a good place to have these conversations, as they go off the rails very quickly. We encourage you to use the Round Table instead, where it is much more clear that all posts need to be serious.
-----------------------------
10. MAA complaints: discouraged
We don't want to pretend that the MAA is perfect or that we agree with everything they do. However, we chose to discourage this sort of behavior because in practice most of the comments we see are not useful and some are frankly offensive.
[list] [*] If you just want to blow off steam, do it on your blog instead.
[*] When you have criticism, it should be reasoned, well-thought and constructive. What we mean by this is, for example, when the AOIME was announced, there was great outrage about potential cheating. Well, do you really think that this is something the organizers didn't think about too? Simply posting that "people will cheat and steal my USAMOO qualification, the MAA are idiots!" is not helpful as it is not bringing any new information to the table.
[*] Even if you do have reasoned, well-thought, constructive criticism, we think it is actually better to email it the MAA instead, rather than post it here. Experience shows that even polite, well-meaning suggestions posted in C&P are often derailed by less mature users who insist on complaining about everything.
[/list]
-----------------------------
11. Memes and joke posts: discouraged
It's fine to make jokes or lighthearted posts every so often. But it should be done with discretion. Ideally, jokes should be done within a longer post that has other content. For example, in my response to one user's question about olympiad combinatorics, I used a silly picture of Sogiita Gunha, but it was done within a context of a much longer post where it was meant to actually make a point.

On the other hand, there are many threads which consist largely of posts whose only content is an attached meme with the word "MAA" in it. When done in excess like this, the jokes reflect poorly on the community, so we explicitly discourage them.
-----------------------------
12. Questions that no one can answer: discouraged
Examples of this: "will MIT ask for AOIME scores?", "what will the AIME 2021 cutoffs be (asked in 2020)", etc. Basically, if you ask a question on this forum, it's better if the question is something that a user can plausibly answer :)
-----------------------------
13. Blind speculation: discouraged
Along these lines, if you do see a question that you don't have an answer to, we discourage "blindly guessing" as it leads to spreading of baseless rumors. For example, if you see some user posting "why are there fewer qualifiers than usual this year?", you should not reply "the MAA must have been worried about online cheating so they took fewer people!!". Was sich überhaupt sagen lässt, lässt sich klar sagen; und wovon man nicht reden kann, darüber muss man schweigen.
-----------------------------
14. Discussion of cheating: strongly discouraged
If you have evidence or reasonable suspicion of cheating, please report this to your Competition Manager or to the AMC HQ; these forums cannot help you.
Otherwise, please avoid public discussion of cheating. That is: no discussion of methods of cheating, no speculation about how cheating affects cutoffs, and so on --- it is not helpful to anyone, and it creates a sour atmosphere. A longer explanation is given in Seriously, please stop discussing how to cheat.
-----------------------------
15. Cutoff jokes: never allowed
Whenever the cutoffs for any major contest are released, it is very obvious when they are official. In the past, this has been achieved by the numbers being posted on the official AMC website (here) or through a post from the AMCDirector account.

You must never post fake cutoffs, even as a joke. You should also refrain from posting cutoffs that you've heard of via email, etc., because it is better to wait for the obvious official announcement. A longer explanation is given in A Treatise on Cutoff Trolling.
-----------------------------
16. Meanness: never allowed
Being mean is worse than being immature and unproductive. If another user does something which you think is inappropriate, use the Report button to bring the post to moderator attention, or if you really must reply, do so in a way that is tactful and constructive rather than inflammatory.
-----------------------------

Finally, we remind you all to sit back and enjoy the problems. :D

-----------------------------
(EDIT 2024-09-13: AoPS has asked to me to add the following item.)

Advertising paid program or service: never allowed

Per the AoPS Terms of Service (rule 5h), general advertisements are not allowed.

While we do allow advertisements of official contests (at the MAA and MATHCOUNTS level) and those run by college students with at least one successful year, any and all advertisements of a paid service or program is not allowed and will be deleted.
0 replies
v_Enhance
Jun 12, 2020
0 replies
k i Stop looking for the "right" training
v_Enhance   50
N Oct 16, 2017 by blawho12
Source: Contest advice
EDIT 2019-02-01: https://blog.evanchen.cc/2019/01/31/math-contest-platitudes-v3/ is the updated version of this.

EDIT 2021-06-09: see also https://web.evanchen.cc/faq-contest.html.

Original 2013 post
50 replies
v_Enhance
Feb 15, 2013
blawho12
Oct 16, 2017
circle geometry showing perpendicularity
Kyj9981   2
N 7 minutes ago by Double07
Two circles $\omega_1$ and $\omega_2$ intersect at points $A$ and $B$. A line through $B$ intersects $\omega_1$ and $\omega_2$ at points $C$ and $D$, respectively. Line $AD$ intersects $\omega_1$ at point $E \neq A$, and line $AC$ intersects $\omega_2$ at point $F \neq A$. If $O$ is the circumcenter of $\triangle AEF$, prove that $OB \perp CD$.
2 replies
Kyj9981
Today at 11:53 AM
Double07
7 minutes ago
Diophantine equation
PaperMath   9
N 8 minutes ago by gaussiemann144
Find the $5$ smallest positive solutions of $x$ that has an integer $k$ that satisfies $x^2=3k^2+4$
9 replies
PaperMath
Mar 12, 2025
gaussiemann144
8 minutes ago
The return of American geo
brianzjk   78
N 10 minutes ago by Ilikeminecraft
Source: USAJMO 2023/6
Isosceles triangle $ABC$, with $AB=AC$, is inscribed in circle $\omega$. Let $D$ be an arbitrary point inside $BC$ such that $BD\neq DC$. Ray $AD$ intersects $\omega$ again at $E$ (other than $A$). Point $F$ (other than $E$) is chosen on $\omega$ such that $\angle DFE = 90^\circ$. Line $FE$ intersects rays $AB$ and $AC$ at points $X$ and $Y$, respectively. Prove that $\angle XDE = \angle EDY$.

Proposed by Anton Trygub
78 replies
brianzjk
Mar 23, 2023
Ilikeminecraft
10 minutes ago
[Registration Open] Mustang Math Tournament 2025
MustangMathTournament   36
N 28 minutes ago by wuwang2002
Mustang Math is excited to announce that registration for our annual tournament, MMT 2025, is open! This year, we are bringing our tournament to 9 in-person locations, as well as online!

Locations include: Colorado, Norcal, Socal, Georgia, Illinois, Massachusetts, New Jersey, Nevada, Washington, and online. For registration and more information, check out https://mustangmath.com/competitions/mmt-2025.

MMT 2025 is a math tournament run by a group of 150+ mathematically experienced high school and college students who are dedicated to providing a high-quality and enjoyable contest for middle school students. Our tournament centers around teamwork and collaboration, incentivizing students to work with their teams not only to navigate the challenging and interesting problems of the tournament but also to develop strategies to master the unique rounds. This includes a logic puzzle round, a strategy-filled hexes round, a race-like gallop round, and our trademark ‘Mystery Mare’ round!

Awards:
[list]
[*] Medals for the top teams
[*] Shirts, pins, stickers and certificates for all participants
[*] Additional awards provided by our wonderful sponsors!
[/list]

We are also holding a free MMT prep seminar from 3/15-3/16 to help students prepare for the upcoming tournament. Join the Google Classroom! https://classroom.google.com/c/NzQ5NDUyNDY2NjM1?cjc=7sogth4
36 replies
MustangMathTournament
Mar 8, 2025
wuwang2002
28 minutes ago
AMC 12 Question
sadas123   6
N 29 minutes ago by gavinhaominwang
Hello! I am a 6th grader this year about to become 7th grade next year. I was wondering if I should take the AMC 12 next year because I think I am ready for it, I was thinking to do AMC 10 A and AMC 12 B, do you think it is a good idea? Here are the courses I finished and now I am working on:

Finished:
1. Intro Algebra
2. Intro Number Theory
3. Intro Counting and Probability
4. Volume 1

Working on:
1. Intermdiate Counting and Probability
2. Three Year Mathcounts Marathon

Upcoming:
1. Intro Geomtery (Next Month)
2. Intro to Alg (May)
3. Pre-calc (Summer)
4. Volume 2???

Stats for AMC 12 (Mocked):

1. AMC 12 A 2024: 100.5
2. AMC 12 B 2024: 105
3. AMC 12 A 2023: 96

The reason why I sometimes I get 100+ is because sometimes I know how to do the first step of the problem but the last step I have to kind of infrence but still i know how to do the problem.
6 replies
sadas123
2 hours ago
gavinhaominwang
29 minutes ago
How many ordered pairs of numbers can we find?
BR1F1SZ   2
N 38 minutes ago by BR1F1SZ
Source: 2024 Argentina TST P6
Given $2024$ non-negative real numbers $x_1, x_2, \dots, x_{2024}$ that satisfy $x_1 + x_2 + \cdots + x_{2024} = 1$, determine the maximum possible number of ordered pairs $(i, j)$ such that
\[
x_i^2 + x_j \geqslant \frac{1}{2023}.
\]
2 replies
BR1F1SZ
Jan 25, 2025
BR1F1SZ
38 minutes ago
IMO 2009, Problem 5
orl   87
N 43 minutes ago by asdf334
Source: IMO 2009, Problem 5
Determine all functions $ f$ from the set of positive integers to the set of positive integers such that, for all positive integers $ a$ and $ b$, there exists a non-degenerate triangle with sides of lengths
\[ a, f(b) \text{ and } f(b + f(a) - 1).\]
(A triangle is non-degenerate if its vertices are not collinear.)

Proposed by Bruno Le Floch, France
87 replies
+1 w
orl
Jul 16, 2009
asdf334
43 minutes ago
Apply for Team USA at the International Math Competition (IMC)!
peace09   54
N 2 hours ago by profhong
The International Math Competition (IMC) is essentially the elementary and middle school equivalent of the IMO, with individual and team rounds featuring both short-answer and proof-based problems. See past problems here.

Team USA is looking for 6th graders and below with AIME qualification or AMC 8 DHR (or equivalent), and for 9th graders and below with JMO or Mathcounts Nationals qualification. If you think you meet said criteria, fill out the initial form here.

Here are a couple quick links for further information:
[list=disc]
[*] Dr. Tao Hong's website, which contains a detailed recap of the 2024 competition (and previous years'), as well as Team USA's historical results. (You may recognize a couple names... @channing421 @vrondoS et al.: back me up here :P)
[*] My journal, which gives an insider's perspective on the camp :ninja:
[/list]
54 replies
peace09
Aug 13, 2024
profhong
2 hours ago
AIME score for college apps
Happyllamaalways   85
N 3 hours ago by MC_ADe
What good colleges do I have a chance of getting into with an 11 on AIME? (Any chances for Princeton)

Also idk if this has weight but I had the highest AIME score in my school.
85 replies
Happyllamaalways
Mar 13, 2025
MC_ADe
3 hours ago
AMC 10.........
BAM10   11
N 3 hours ago by Andyluo
I'm in 8th grade and have never taken the AMC 10. I am currently in alg2. I have scored 20 on AMC 8 this year and 34 on the chapter math counts last year. Can I qualify for AIME. Also what should I practice AMC 10 next year?
11 replies
BAM10
Mar 2, 2025
Andyluo
3 hours ago
rows are DERANGED and a SOCOURGE to usajmo .
GrantStar   27
N 3 hours ago by EGMO
Source: USAJMO 2024/4
Let $n \geq 3$ be an integer. Rowan and Colin play a game on an $n \times n$ grid of squares, where each square is colored either red or blue. Rowan is allowed to permute the rows of the grid and Colin is allowed to permute the columns. A grid coloring is orderly if: [list] [*]no matter how Rowan permutes the rows of the coloring, Colin can then permute the columns to restore the original grid coloring; and [*]no matter how Colin permutes the columns of the coloring, Rowan can then permute the rows to restore the original grid coloring. [/list] In terms of $n$, how many orderly colorings are there?

Proposed by Alec Sun
27 replies
GrantStar
Mar 21, 2024
EGMO
3 hours ago
Cooked for AMC 10?
Dream9   3
N 4 hours ago by bhontu
So I'm like a 8th grader so almost 9th over the summer and I suck at AMC 10. I got like a 75 for my first time but I can do like almost all the problems from AMC 8 with enough time which I find really weird because most other ppl who can do that get higher AMC 10 scores. I do like the first 11 problems a day from past years to try to at least get down the first 10 questions and move on from there. Does anyone have any good suggestions on how I can boost my AMC 10 scores?
+ something annoying that often happens is like I don't even know where to start when I see a problem.
3 replies
Dream9
Mar 16, 2025
bhontu
4 hours ago
10B Score Thread
BS2012   134
N 5 hours ago by pingpongmerrily
$\begin{tabular}{c|c|c|c|c}Username & Grade & 10B \\ \hline
BS2012 & 9 & 144  \\
\end{tabular}$
EDIT: I found out i didn't silly #19, so i got 144
134 replies
BS2012
Nov 13, 2024
pingpongmerrily
5 hours ago
Redflame2112 would like to know your location
john0512   62
N Today at 1:32 PM by cj13609517288
Source: AMC 10A 2021/1
What is the value of $\frac{(2112-2021)^2}{169}$?

$\textbf{(A) }7\qquad\textbf{(B) }21\qquad\textbf{(C) }49\qquad\textbf{(D) }64\qquad\textbf{(E) }91$
62 replies
john0512
Nov 11, 2021
cj13609517288
Today at 1:32 PM
JBMO Shortlist 2023 C1
Orestis_Lignos   6
N Today at 12:28 AM by zhenghua
Source: JBMO Shortlist 2023, C1
Given is a square board with dimensions $2023 \times 2023$, in which each unit cell is colored blue or red. There are exactly $1012$ rows in which the majority of cells are blue, and exactly $1012$ columns in which the majority of cells are red.

What is the maximal possible side length of the largest monochromatic square?
6 replies
Orestis_Lignos
Jun 28, 2024
zhenghua
Today at 12:28 AM
JBMO Shortlist 2023 C1
G H J
G H BBookmark kLocked kLocked NReply
Source: JBMO Shortlist 2023, C1
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Orestis_Lignos
555 posts
#1 • 2 Y
Y by ItsBesi, lian_the_noob12
Given is a square board with dimensions $2023 \times 2023$, in which each unit cell is colored blue or red. There are exactly $1012$ rows in which the majority of cells are blue, and exactly $1012$ columns in which the majority of cells are red.

What is the maximal possible side length of the largest monochromatic square?
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Assassino9931
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#3
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Answer

Bound

Example
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crezk
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Y by ehuseyinyigit
generalization for $(2n+1)^2$ is $n$
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ItsBesi
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Finally did a combi :)

Answer: $2011$

Bounding:

Let $X$ be the length of the largest monochromatic square.

FTSOC assume $X \geq 2012$

Assume that the color in the monochromatic square is blue so if $X \geq 2012$ note that because of the square there should be $1012$ rows which are blue and also $1012$ columns that are also blue hence there are $2023-1012=1011$ columns that the majority of cells are red but this is a contradiction by our condition . $\rightarrow \leftarrow$

Hence $X <2012 \iff X \leq 2011$

Now we just show that $X=2011$ works:

Construction
Attachments:
This post has been edited 1 time. Last edited by ItsBesi, Jan 29, 2025, 10:47 AM
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Mhremath
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#6
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easy
Let's say this square AZ Square

now Let's AZ square side be $A$
$\textcolor{red}{Claim:}$ There is no way that $A\geq 1012$
proof:
that's easy to show according to the our AZ square includes oly the same colored unit cells
and we know that majority of the rows and columns $A>1012$ is Absurd
and$A=1012$ contradict majority
then A=1011 is our answer and there is no any contradiction

and here is some cells
This post has been edited 1 time. Last edited by Mhremath, Jan 30, 2025, 8:28 PM
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jasperE3
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#8
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Orestis_Lignos wrote:
Given is a square board with dimensions $2023 \times 2023$, in which each unit cell is colored blue or red. There are exactly $1012$ rows in which the majority of cells are blue, and exactly $1012$ columns in which the majority of cells are red.

What is the maximal possible side length of the largest monochromatic square?
Call a row or column red-dominated if it has at least $c$ red cells (id est, the majority of the cells are red), and define blue-dominated similarly. Note that each row and column is either red-dominated or blue-dominated since each row and column has an odd number $2c+1$ of cells.

We will show that the answer is $1011$, by proving the following generalized problem for special case $c=1011$.
generalized problem wrote:
Let $c\in\mathbb N$. Given is a square board with dimensions $(2c+1)\times(2c+1)$, in which each unit cell is colored blue or red. There are exactly $c+1$ blue-dominated rows, and exactly $c+1$ red-dominated columns.

Prove that the maximal possible side length of the largest monochromatic square is $c$.
For the construction, we assign coordinates $(i,j)$ to each cell, where $1\le i\le2c+1$ is the column number and $1\le j\le2c+1$ is the row number. This is formally defined recursively by the following:
  1. $(1,1)$ is the bottom-left-most cell in the board
  2. if $1\le i\le2c+1$ and $1\le j\le2c$ then the cell $(i,j+1)$ is the cell directly above the cell $(i,j)$
  3. if $1\le i\le2c$ and $1\le j\le2c+1$ then the cell $(i+1,j)$ is the cell directly to the right of the cell $(i,j)$
We use the following coloring: color cell $(i,j)$ blue if $1\le i,j\le2c+1$ and one of the following mutually exclusive conditions are met:
  1. $i=j\le c+1$
  2. $i\ge c+2$ and $j\le c+1$
Color it red otherwise.

For example, this is the coloring for $c=6$:
https://i.ibb.co/rGsvcrFJ/pixil-frame-0-2.png

This works because:
  • there is a monochromatic blue $c\times c$ square in the bottom-right of the board, at coordinates $c+2\le i\le2c+1$, $1\le j\le c+1$ (as well as another blue $c\times c$ square one unit above that, and $c+2$ red $c\times c$ squares along the top of the board)
  • there are $c+1$ blue-dominated rows at coordinates $1\le j\le c+1$, since each of these rows will have $1$ blue cell at $i\le c+1$ that follow condition $A$ above, and $2c-(c+2)+1=c-1$ blue cells at $i\ge c+2$ following condition $B$
  • there are $c$ red-dominated rows (meaning that there cannot be more than $c+1$ blue-dominated rows) at coordinates $c+2\le j\le2c+1$, since they don't follow conditions $A$ or $B$
  • there are $c+1$ red-dominated columns at coordinates $1\le i\le c+1$, since each of these columns will have $1$ blue cell following condition $A$ and no other blue cells
  • there are $c$ blue-dominated columns (meaning that there cannot be more than $c+1$ red-dominated rows) at coordinates $c+2\le i\le2c+1$, since each of these columns have $c+1$ blue cells following condition $B$


Now suppose that it is possible to have a monochromatic $(c+1)\times(c+1)$ square.

If the square were red, then each of the $c+1$ rows of the board that intersect the square would have $c+1$ red cells, and therefore be red-dominated. But since the problem statement requires us to have at least $c+1$ blue-dominated rows, this would require us to have $(c+1)+(c+1)>2c+1$ rows, contradiction.

Likewise, if the square were blue, each of the $c+1$ columns that intersect the square would be blue-dominated, which is impossible as the problem requires exactly $c+1$ red-dominated columns.

So it is impossible to have a monochromatic $(c+1)\times(c+1)$ square in such a $(2c+1)\times(2c+1)$ board, and the largest possible such monochromatic square is indeed $c\times c$.
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zhenghua
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Let's generalize this by turning $2023\rightarrow 2n+1$ where $n>1$. Then there must be $n+1$ rows where the majority of the cells are blue, and exactly $n+1$ columns where the majority of the cells are red.

We claim the answer is a monochromatic square of size $n.$ The below configuration works for any $n>1$.
[asy]

fill((0,0)--(0,7)--(7,7)--(7,0)--cycle, blue);
fill((0,0)--(1,0)--(1,7)--(0,7)--cycle, red);
fill((4,0)--(7,0)--(7,3)--(4,3)--cycle, red);
fill((4,3)--(5,3)--(5,4)--(4,4)--cycle, red);
fill((5,4)--(6,4)--(6,5)--(5,5)--cycle, red);
fill((6,5)--(7,5)--(7,6)--(6,6)--cycle, red);

add(grid(7,7));

draw((4,0)--(7,0)--(7,3)--(4,3)--cycle, green);

[/asy]

Now we prove that any monochromatic square with a size more than $n$ violates one of the conditions. WLOG, let the color of the square be red and have side length $n+1$. Now note that $n+1>\frac{2n+1}{2}$ so there can be a maximum of $n$ columns with a majority of blue squares. However, this contradicts since we need exactly $n+1$ columns with a majority of blue squares. Thus, contradiction. Therefore the answer is $n$.

This problem is when $n=1011$ so the answer is $\boxed{1011}$.

$\mathbb{Q.E.D.}$
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