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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]
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
May 1, 2025
0 replies
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
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
IMO ShortList 1999, geometry problem 2
orl   13
N 41 minutes ago by ezpotd
Source: IMO ShortList 1999, geometry problem 2
A circle is called a separator for a set of five points in a plane if it passes through three of these points, it contains a fourth point inside and the fifth point is outside the circle. Prove that every set of five points such that no three are collinear and no four are concyclic has exactly four separators.
13 replies
orl
Nov 13, 2004
ezpotd
41 minutes ago
Brilliant Problem
M11100111001Y1R   5
N an hour ago by Davdav1232
Source: Iran TST 2025 Test 3 Problem 3
Find all sequences \( (a_n) \) of natural numbers such that for every pair of natural numbers \( r \) and \( s \), the following inequality holds:
\[
\frac{1}{2} < \frac{\gcd(a_r, a_s)}{\gcd(r, s)} < 2
\]
5 replies
+1 w
M11100111001Y1R
May 27, 2025
Davdav1232
an hour ago
4 var inequality
SunnyEvan   0
an hour ago
Source: Own
Let $ x,y,z,t \in R^+ ,$ such that : $ (x+y+z+t)^2 = x+y+z+t + (x+z)(y+t) $ and $ x \geq y \geq z \geq t .$
Try to prove or disprove : $$ \frac{2 \sqrt{x+y+z+t +(x+t)(y+z)}}{x^2+y^2+z^2+t^2 +3xz+3yt+xt+yz} \geq \frac{11(x+z)(z+t)-(x+y+z+t)}{x+y+z+t +(x+z)(y+t)} $$
0 replies
SunnyEvan
an hour ago
0 replies
Simple inequality
sqing   60
N an hour ago by Adywastaken
Source: Shortlist BMO 2018, A1
Let $a, b, c $ be positive real numbers such that $abc = \frac {2} {3}. $ Prove that:

$$\frac {ab}{a + b} + \frac {bc} {b + c} + \frac {ca} {c + a} \geqslant  \frac {a+b+c} {a^3+b ^ 3 + c ^ 3}.$$
60 replies
sqing
May 3, 2019
Adywastaken
an hour ago
Serbian selection contest for the IMO 2025 - P6
OgnjenTesic   13
N an hour ago by JARP091
Source: Serbian selection contest for the IMO 2025
For an $n \times n$ table filled with natural numbers, we say it is a divisor table if:
- the numbers in the $i$-th row are exactly all the divisors of some natural number $r_i$,
- the numbers in the $j$-th column are exactly all the divisors of some natural number $c_j$,
- $r_i \ne r_j$ for every $i \ne j$.

A prime number $p$ is given. Determine the smallest natural number $n$, divisible by $p$, such that there exists an $n \times n$ divisor table, or prove that such $n$ does not exist.

Proposed by Pavle Martinović
13 replies
OgnjenTesic
May 22, 2025
JARP091
an hour ago
A sharp one with 3 var (3)
mihaig   5
N an hour ago by JARP091
Source: Own
Let $a,b,c\geq0$ satisfying
$$\left(a+b+c-2\right)^2+8\leq3\left(ab+bc+ca\right).$$Prove
$$a^2+b^2+c^2+5abc\geq8.$$
5 replies
mihaig
Tuesday at 5:17 PM
JARP091
an hour ago
IMO 2016 Problem 1
quangminhltv99   152
N an hour ago by MTA_2024
Source: IMO 2016
Triangle $BCF$ has a right angle at $B$. Let $A$ be the point on line $CF$ such that $FA=FB$ and $F$ lies between $A$ and $C$. Point $D$ is chosen so that $DA=DC$ and $AC$ is the bisector of $\angle{DAB}$. Point $E$ is chosen so that $EA=ED$ and $AD$ is the bisector of $\angle{EAC}$. Let $M$ be the midpoint of $CF$. Let $X$ be the point such that $AMXE$ is a parallelogram. Prove that $BD,FX$ and $ME$ are concurrent.
152 replies
1 viewing
quangminhltv99
Jul 11, 2016
MTA_2024
an hour ago
Circles with Altitude Feet
tastymath75025   32
N 2 hours ago by Aiden-1089
Source: 2019 ELMO Shortlist G4
Let triangle $ABC$ have altitudes $BE$ and $CF$ which meet at $H$. The reflection of $A$ over $BC$ is $A'$. Let $(ABC)$ meet $(AA'E)$ at $P$ and $(AA'F)$ at $Q$. Let $BC$ meet $PQ$ at $R$. Prove that $EF \parallel HR$.

Proposed by Daniel Hu
32 replies
tastymath75025
Jun 27, 2019
Aiden-1089
2 hours ago
Not so beautiful
m4thbl3nd3r   2
N 2 hours ago by m4thbl3nd3r
Let $a, b,c>0$ such that $b+c>a$. Prove that $$2 \sqrt[4]{\frac{a}{b+c-a}}\ge 2 +\frac{2a^2-b^2-c^2}{(a+b)(a+c)}.$$
2 replies
m4thbl3nd3r
5 hours ago
m4thbl3nd3r
2 hours ago
Concurrent lines, angle bisectors
legogubbe   1
N 2 hours ago by Captainscrubz
Source: ???
Hi AoPS!

Let $ABC$ be an isosceles triangle with $AB=AC$, and $M$ an arbitrary point on side $BC$. The internal angle bisector of $\angle MAB$ meets the circumcircle of $\triangle ABC$ again at $P \neq A$, and the internal angle bisector of $\angle CAM$ meets it again at $Q \neq A$. Show that lines $AM$, $BQ$ and $CP$ are concurrent.
1 reply
legogubbe
Yesterday at 11:09 PM
Captainscrubz
2 hours ago
9 Mock AMC 8
Leeoz   2
N 3 hours ago by Yihangzh
This is just your average mock AMC 8 on AoPS... nothing sus at all...
Just PM me your answers if you actually want to try it and be on the leaderboard...

Leaderboard

This test is for entertainment purposes only...

Also if you all want, I can post the solutions in June.
2 replies
Leeoz
3 hours ago
Yihangzh
3 hours ago
Trivial Factoring MathCounts Question? 2025 MathCounts National Sprint Round #29
ilikemath247365   28
N 4 hours ago by Schintalpati
What is the value of the expression below?

$\frac{(1! + 2! + 3!)(2! + 3! + 4!)(3! + 4! + 5!)...(98! + 99! + 100!)}{(1! - 3(2!) + 3!)(2! - 3(3!) + 4!)(3! - 3(4!) + 5!)...(98! - 3(99!) + 100!)}$.
28 replies
ilikemath247365
Yesterday at 1:16 AM
Schintalpati
4 hours ago
Overly wordy problems
ZMB038   4
N 5 hours ago by CJB19
Hey everyone, here we can post questions with way to many extraneous words, that are actually easy.
Try to solve the one above yours.
I'll start:
Click to reveal hidden text
4 replies
ZMB038
Yesterday at 11:14 PM
CJB19
5 hours ago
Math with Connect4 Boards
Math-lover1   7
N 6 hours ago by CJB19
Hi! So I was playing Connect4 with my friends the other day and I wondered: how many "legal" arrangements of Connect4 can be reached at the ending position?

We assume that we do not stop the game when there is a four in a row, and we have 21 red pieces and 21 yellow pieces. We also drop the pieces one by one into a standard 7 by 6 board. We can start the game with any color piece.

https://en.wikipedia.org/wiki/Connect_Four

Initial Thoughts
Attempt to use one-to-one correspondences
7 replies
Math-lover1
May 1, 2025
CJB19
6 hours ago
The daily problem!
Leeoz   210
N Today at 1:30 AM by sadas123
Every day, I will try to post a new problem for you all to solve! If you want to post a daily problem, you can! :)

Please hide solutions and answers, hints are fine though! :)

Problems usually get harder throughout the week, so Sunday is the easiest and Saturday is the hardest!

Past Problems!
210 replies
Leeoz
Mar 21, 2025
sadas123
Today at 1:30 AM
The daily problem!
G H J
G H BBookmark kLocked kLocked NReply
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complex0
12 posts
#210
Y by
Inaaya wrote:
How many ways are there to arrange the word HAPPYBIRTHDAY such that the 3 a's are together, and the two p's are not next to each other
Click to reveal hidden text
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Inaaya
423 posts
#211
Y by
complex0 wrote:
Inaaya wrote:
How many ways are there to arrange the word HAPPYBIRTHDAY such that the 3 a's are together, and the two p's are not next to each other
Click to reveal hidden text

my bad :skull:
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ForeverSnow
66 posts
#212
Y by
"DAILY?"
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complex0
12 posts
#213
Y by
Inaaya wrote:
complex0 wrote:
Inaaya wrote:
How many ways are there to arrange the word HAPPYBIRTHDAY such that the 3 a's are together, and the two p's are not next to each other
Click to reveal hidden text

my bad :skull:
lol ur good
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complex0
12 posts
#214
Y by
What is the remainder when:
$1^1$ $+$ $2^2$ $+$ $3^3$ $+$ $\cdots$ $+$ $2025^{2025}$ / $\sum_{k=1}^{2025} k^k$ is divided by 2025?
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SpeedCuber7
1870 posts
#215
Y by
sol
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sadas123
1326 posts
#216
Y by
Solution
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pieMax2713
4227 posts
#217
Y by
sadas123 wrote:
Solution

no explanation whatsoever how that's 1 mod 2025?
also you're both wrong the answer is this according to wolfram
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Shan3t
430 posts
#218
Y by
pieMax2713 wrote:
sadas123 wrote:
Solution

no explanation whatsoever how that's 1 mod 2025?
also you're both wrong the answer is this according to wolfram

the $/$ is for division im pretty sure
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elizhang101412
1270 posts
#219
Y by
Shan3t wrote:
pieMax2713 wrote:
sadas123 wrote:
Solution

no explanation whatsoever how that's 1 mod 2025?
also you're both wrong the answer is this according to wolfram

the $/$ is for division im pretty sure

me when i know summation in latex but i dont know division
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pieMax2713
4227 posts
#220
Y by
you would expect if they knew summation notation in latex they would know something as simple as fraction notation and denote it clearly
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wipid98
76 posts
#221
Y by
$\sqrt \frac{\sqrt\frac{ax}{a-x}\cdot A\frac{a}{ax}}{x^2a^2}=10$
solve for $ a $. round to the nearest decimal
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complex0
12 posts
#222
Y by
sry if i made it unclear the / is NOT division its just another way to write it
I realized now that it was stupid and made it unclear
sorry guys
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Soupboy0
512 posts
#223
Y by
complex0 wrote:
What is the remainder when:
$1^1$ $+$ $2^2$ $+$ $3^3$ $+$ $\cdots$ $+$ $2025^{2025}$ / $\sum_{k=1}^{2025} k^k$ is divided by 2025?

is there an actual way to do this
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sadas123
1326 posts
#224
Y by
complex0 wrote:
sry if i made it unclear the / is NOT division its just another way to write it
I realized now that it was stupid and made it unclear
sorry guys

oh wait I thought it was division that is why I put 1 because they are the same :skull
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