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k a May Highlights and 2025 AoPS Online Class Information
jlacosta   0
May 1, 2025
May is an exciting month! National MATHCOUNTS is the second week of May in Washington D.C. and our Founder, Richard Rusczyk will be presenting a seminar, Preparing Strong Math Students for College and Careers, on May 11th.

Are you interested in working towards MATHCOUNTS and don’t know where to start? We have you covered! If you have taken Prealgebra, then you are ready for MATHCOUNTS/AMC 8 Basics. Already aiming for State or National MATHCOUNTS and harder AMC 8 problems? Then our MATHCOUNTS/AMC 8 Advanced course is for you.

Summer camps are starting next month at the Virtual Campus in math and language arts that are 2 - to 4 - weeks in duration. Spaces are still available - don’t miss your chance to have an enriching summer experience. There are middle and high school competition math camps as well as Math Beasts camps that review key topics coupled with fun explorations covering areas such as graph theory (Math Beasts Camp 6), cryptography (Math Beasts Camp 7-8), and topology (Math Beasts Camp 8-9)!

Be sure to mark your calendars for the following upcoming events:
[list][*]May 9th, 4:30pm PT/7:30pm ET, Casework 2: Overwhelming Evidence — A Text Adventure, a game where participants will work together to navigate the map, solve puzzles, and win! All are welcome.
[*]May 19th, 4:30pm PT/7:30pm ET, What's Next After Beast Academy?, designed for students finishing Beast Academy and ready for Prealgebra 1.
[*]May 20th, 4:00pm PT/7:00pm ET, Mathcamp 2025 Qualifying Quiz Part 1 Math Jam, Problems 1 to 4, join the Canada/USA Mathcamp staff for this exciting Math Jam, where they discuss solutions to Problems 1 to 4 of the 2025 Mathcamp Qualifying Quiz!
[*]May 21st, 4:00pm PT/7:00pm ET, Mathcamp 2025 Qualifying Quiz Part 2 Math Jam, Problems 5 and 6, Canada/USA Mathcamp staff will discuss solutions to Problems 5 and 6 of the 2025 Mathcamp Qualifying Quiz![/list]
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0 replies
jlacosta
May 1, 2025
0 replies
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k i Adding contests to the Contest Collections
dcouchman   1
N Apr 5, 2023 by v_Enhance
Want to help AoPS remain a valuable Olympiad resource? Help us add contests to AoPS's Contest Collections.

Find instructions and a list of contests to add here: https://artofproblemsolving.com/community/c40244h1064480_contests_to_add
1 reply
dcouchman
Sep 9, 2019
v_Enhance
Apr 5, 2023
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k i Zero tolerance
ZetaX   49
N May 4, 2019 by NoDealsHere
Source: Use your common sense! (enough is enough)
Some users don't want to learn, some other simply ignore advises.
But please follow the following guideline:


To make it short: ALWAYS USE YOUR COMMON SENSE IF POSTING!
If you don't have common sense, don't post.


More specifically:

For new threads:


a) Good, meaningful title:
The title has to say what the problem is about in best way possible.
If that title occured already, it's definitely bad. And contest names aren't good either.
That's in fact a requirement for being able to search old problems.

Examples:
Bad titles:
- "Hard"/"Medium"/"Easy" (if you find it so cool how hard/easy it is, tell it in the post and use a title that tells us the problem)
- "Number Theory" (hey guy, guess why this forum's named that way¿ and is it the only such problem on earth¿)
- "Fibonacci" (there are millions of Fibonacci problems out there, all posted and named the same...)
- "Chinese TST 2003" (does this say anything about the problem¿)
Good titles:
- "On divisors of a³+2b³+4c³-6abc"
- "Number of solutions to x²+y²=6z²"
- "Fibonacci numbers are never squares"


b) Use search function:
Before posting a "new" problem spend at least two, better five, minutes to look if this problem was posted before. If it was, don't repost it. If you have anything important to say on topic, post it in one of the older threads.
If the thread is locked cause of this, use search function.

Update (by Amir Hossein). The best way to search for two keywords in AoPS is to input
[code]+"first keyword" +"second keyword"[/code]
so that any post containing both strings "first word" and "second form".


c) Good problem statement:
Some recent really bad post was:
[quote]$lim_{n\to 1}^{+\infty}\frac{1}{n}-lnn$[/quote]
It contains no question and no answer.
If you do this, too, you are on the best way to get your thread deleted. Write everything clearly, define where your variables come from (and define the "natural" numbers if used). Additionally read your post at least twice before submitting. After you sent it, read it again and use the Edit-Button if necessary to correct errors.


For answers to already existing threads:


d) Of any interest and with content:
Don't post things that are more trivial than completely obvious. For example, if the question is to solve $x^{3}+y^{3}=z^{3}$, do not answer with "$x=y=z=0$ is a solution" only. Either you post any kind of proof or at least something unexpected (like "$x=1337, y=481, z=42$ is the smallest solution). Someone that does not see that $x=y=z=0$ is a solution of the above without your post is completely wrong here, this is an IMO-level forum.
Similar, posting "I have solved this problem" but not posting anything else is not welcome; it even looks that you just want to show off what a genius you are.

e) Well written and checked answers:
Like c) for new threads, check your solutions at least twice for mistakes. And after sending, read it again and use the Edit-Button if necessary to correct errors.



To repeat it: ALWAYS USE YOUR COMMON SENSE IF POSTING!


Everything definitely out of range of common sense will be locked or deleted (exept for new users having less than about 42 posts, they are newbies and need/get some time to learn).

The above rules will be applied from next monday (5. march of 2007).
Feel free to discuss on this here.
49 replies
ZetaX
Feb 27, 2007
NoDealsHere
May 4, 2019
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Nice problem
Martin.s   1
N 33 minutes ago by cazanova19921
If \(p\) is a prime and \(n \geq p\), then
\[ n! \sum_{pi+j=n} \frac{1}{p^i i! j!} \equiv 0 \pmod{p}. \]
1 reply
Martin.s
Yesterday at 6:46 PM
cazanova19921
33 minutes ago
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Interesting geometry problem
DrAymeinstein   3
N 42 minutes ago by Rayvhs
Source: Moroccan TST 2019 P6
Let $ABC$ be a triangle. The tangent in $A$ of the circumcircle of $ABC$ cuts the line $(BC)$ in $X$. Let $A'$ be the symetric of $A$ by $X$ and $C'$ the symetric of $C$ by the line $(AX)$
Prove that the points $A, C', A'$ and $B$ are concyclic.
3 replies
DrAymeinstein
Aug 23, 2024
Rayvhs
42 minutes ago
J
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The next problem
SlovEcience   0
an hour ago
Let the sequence be defined as follows:
\[ f_1 = 1, f_{2n} = 3f_n, f_{2n+1} = f_{2n} + 1. \]Find the value of \( f_{100} \).
Can someone help me solve this problem by using a base numeral system?
0 replies
SlovEcience
an hour ago
0 replies
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small problem
sadwinter   0
an hour ago
Source: own
Let $0\leq a,b \leq1$. Prove that
$0\leq(a+2b)^2-4a(4b-a-3ab^2)(2a^2+b^2)\leq9$
0 replies
1 viewing
sadwinter
an hour ago
0 replies
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Circle Midpoint Config
Fuyuki   0
an hour ago
In triangle ABC, point D is the midpoint of BC. Let the second intersection of AD and (ABC) be E. Then, F is the intersection of EC and AB. G is the intersection of BE and AC. Prove that BC is parallel to FG.
0 replies
Fuyuki
an hour ago
0 replies
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IMO ShortList 2001, combinatorics problem 4
orl   13
N 2 hours ago by Aiden-1089
Source: IMO ShortList 2001, combinatorics problem 4
A set of three nonnegative integers $\{x,y,z\}$ with $x < y < z$ is called historic if $\{z-y,y-x\} = \{1776,2001\}$. Show that the set of all nonnegative integers can be written as the union of pairwise disjoint historic sets.
13 replies
orl
Sep 30, 2004
Aiden-1089
2 hours ago
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AIME Resources
senboy   0
2 hours ago
I am currently in 6th grade and am about halfway done with the intro to algebra class. I plan to take the intro to geometry class, and self study from the intro to counting and probability book, aops volume 1, and competition math for middle school by the end of next year(before amc). I mock about a 18-20 on the amc 8, and I don't really know what my amc 10/12 score would be. I'm aiming for at least a DHR next year in amc 8 and hopefully aime qual(btw I live in australia)
1) would I need to to the intermediate series and/or aops volume 2 for aime qual?
2)What are some books that would really help me prep for amc10/12 and aime?
3)what are some specific topics that you think would be useful for me to cover for aime qual?
4) Should I also do intro to number theory or is that not necessary?
0 replies
senboy
2 hours ago
0 replies
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A weird problem
jayme   0
3 hours ago
Dear Mathlinkers,

1. ABC a triangle
2. 0 the circumcircle
3. I the incenter
4. 1 a circle passing througn B and C
5. X, Y the second points of intersection of 1 wrt BI, CI
6. 2 the circumcircle of the triangle XYI
7. M, N the symetrics of B, C wrt XY.

Question : if 2 is tangent to 0 then, 2 is tangent to MN.

Sincerely
Jean-Louis
0 replies
1 viewing
jayme
3 hours ago
0 replies
J
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NT game with products
Kimchiks926   4
N 3 hours ago by math-olympiad-clown
Source: Baltic Way 2022, Problem 20
Ingrid and Erik are playing a game. For a given odd prime $p$, the numbers $1, 2, 3, ..., p-1$ are written on a blackboard. The players take turns making moves with Ingrid starting. A move consists of one of the players crossing out a number on the board that has not yet been crossed out. If the product of all currently crossed out numbers is $1 \pmod p$ after the move, the player whose move it was receives one point, otherwise, zero points are awarded. The game ends after all numbers have been crossed out.

The player who has received the most points by the end of the game wins. If both players have the same score, the game ends in a draw. For each $p$, determine which player (if any) has a winning strategy
4 replies
Kimchiks926
Nov 12, 2022
math-olympiad-clown
3 hours ago
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4th grader qual JMO
HCM2001   53
N 3 hours ago by Yiyj
i mean.. whattttt??? just found out about this.. is he on aops? (i'm sure he is) where are you orz lol..
https://www.mathschool.com/blog/results/celebrating-success-douglas-zhang-is-rsm-s-youngest-usajmo-qualifier
53 replies
HCM2001
May 22, 2025
Yiyj
3 hours ago
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set with c+2a>3b
VicKmath7   49
N 3 hours ago by wangyanliluke
Source: ISL 2021 A1
Let $n$ be a positive integer. Given is a subset $A$ of $\{0,1,...,5^n\}$ with $4n+2$ elements. Prove that there exist three elements $a<b<c$ from $A$ such that $c+2a>3b$.

Proposed by Dominik Burek and Tomasz Ciesla, Poland
49 replies
VicKmath7
Jul 12, 2022
wangyanliluke
3 hours ago
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geo equals ForeBoding For Dennis
dchenmathcounts   99
N 3 hours ago by Yiyj
Source: USAJMO 2020/4
Let $ABCD$ be a convex quadrilateral inscribed in a circle and satisfying $DA < AB = BC < CD$. Points $E$ and $F$ are chosen on sides $CD$ and $AB$ such that $BE \perp AC$ and $EF \parallel BC$. Prove that $FB = FD$.

Milan Haiman
99 replies
dchenmathcounts
Jun 21, 2020
Yiyj
3 hours ago
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interesting geo config (2/3)
Royal_mhyasd   8
N 4 hours ago by Royal_mhyasd
Source: own
Let $\triangle ABC$ be an acute triangle and $H$ its orthocenter. Let $P$ be a point on the parallel through $A$ to $BC$ such that $\angle APH = |\angle ABC-\angle ACB|$. Define $Q$ and $R$ as points on the parallels through $B$ to $AC$ and through $C$ to $AB$ similarly. If $P,Q,R$ are positioned around the sides of $\triangle ABC$ as in the given configuration, prove that $P,Q,R$ are collinear.
8 replies
Royal_mhyasd
Saturday at 11:36 PM
Royal_mhyasd
4 hours ago
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Recommend number theory books
MoonlightNT   8
N 5 hours ago by RocketScientist
I’m preparing AIME and USA(J)MO.
Can you recommend specifically Number theory books?
I already had intro NT of AOSP.
Thank you
8 replies
MoonlightNT
Yesterday at 1:50 PM
RocketScientist
5 hours ago
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Why did my account set back to bronze?
Wisteriaaa   2
N Mar 29, 2025 by ethan2011
Hey, guys! I passed bronze division in Feb 2024 and silver in Jan 2025, but then I found I only could enter bronze division in Feb. What's going wrong with my account? :wacko:
2 replies
Wisteriaaa
Mar 29, 2025
ethan2011
Mar 29, 2025
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Why did my account set back to bronze?
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Reveal topic tags
Usaco
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Wisteriaaa
1 post
Wisteriaaa
#1 h  Mar 29, 2025, 3:02 AM
Y by
Hey, guys! I passed bronze division in Feb 2024 and silver in Jan 2025, but then I found I only could enter bronze division in Feb. What's going wrong with my account? :wacko:
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exp-ipi-1
1074 posts
exp-ipi-1
#2 h  Mar 29, 2025, 3:08 AM
Y by
perhaps you might be cooked
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ethan2011
354 posts
ethan2011
#3 h  Mar 29, 2025, 3:10 AM
Y by
Wisteriaaa wrote:
Hey, guys! I passed bronze division in Feb 2024 and silver in Jan 2025, but then I found I only could enter bronze division in Feb. What's going wrong with my account? :wacko:

Maybe you should send an email to them?
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