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k a April Highlights and 2025 AoPS Online Class Information
jlacosta   0
Apr 2, 2025
Spring is in full swing and summer is right around the corner, what are your plans? At AoPS Online our schedule has new classes starting now through July, so be sure to keep your skills sharp and be prepared for the Fall school year! Check out the schedule of upcoming classes below.

WOOT early bird pricing is in effect, don’t miss out! If you took MathWOOT Level 2 last year, no worries, it is all new problems this year! Our Worldwide Online Olympiad Training program is for high school level competitors. AoPS designed these courses to help our top students get the deep focus they need to succeed in their specific competition goals. Check out the details at this link for all our WOOT programs in math, computer science, chemistry, and physics.

Looking for summer camps in math and language arts? Be sure to check out the video-based summer camps offered at the Virtual Campus that are 2- to 4-weeks in duration. 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 events:
[list][*]April 3rd (Webinar), 4pm PT/7:00pm ET, Learning with AoPS: Perspectives from a Parent, Math Camp Instructor, and University Professor
[*]April 8th (Math Jam), 4:30pm PT/7:30pm ET, 2025 MATHCOUNTS State Discussion
April 9th (Webinar), 4:00pm PT/7:00pm ET, Learn about Video-based Summer Camps at the Virtual Campus
[*]April 10th (Math Jam), 4:30pm PT/7:30pm ET, 2025 MathILy and MathILy-Er Math Jam: Multibackwards Numbers
[*]April 22nd (Webinar), 4:00pm PT/7:00pm ET, Competitive Programming at AoPS (USACO).[/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
Apr 2, 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
2025 MATHCOUNTS State Hub
SirAppel   569
N 2 minutes ago by ethan2011
Previous Years' "Hubs": (2022) (2023) (2024)Please Read

Now that it's April and we're allowed to discuss ...
[list=disc]
[*] CA: 43 (45 44 43 43 43 42 42 41 41 41)
[*] NJ: 43 (45 44 44 43 39 42 40 40 39 38) *
[*] NY: 42 (43 42 42 42 41 40)
[*] TX: 42 (43 43 43 42 42 40 40 38 38 38)
[*] MA: 41 (45 43 42 41)
[*] WA: 41 (41 45 42 41 41 41 41 41 41 40) *
[*]VA: 40 (41 40 40 40)
[*] FL: 39 (42 41 40 39 38 37 37)
[*] IN: 39 (41 40 40 39 36 35 35 35 34 34)
[*] NC: 39 (42 42 41 39)
[*] IL: 38 (41 40 39 38 38 38)
[*] OR: 38 (44 40? 38 38)
[*] PA: 38 (41 40 40 38 38 37 36 36 34 34) *
[*] MD: 37 (43 39 39 37 37 37)
[*] AZ: 36 (40? 39? 39 36)
[*] CT: 36 (44 38 38 36 35 35 34 34 34 33 33)
[*] MI: 36 (39 41 41 36 37 37 36 36 36 36) *
[*] MN: 36 (40 36 36 36 35 35 35 34)
[*] CO: 35 (41 37 37 35 35 35 ?? 31 31 30) *
[*] GA: 35 (38 37 36 35 34 34 34 34 34 33)
[*] OH: 35 (41 37 36 35)
[*] AR: 34 (46 45 35 34 33 31 31 31 29 29)
[*] NV: 34 (41 38 ?? 34)
[*] TN: 34 (38 ?? ?? 34)
[*] WI: 34 (40 37 37 34 35 30 28 29 29 29) *
[*] HI: 32 (35 34 32 32)
[*] NH: 31 (42 35 33 31 30)
[*] DE: 30 (34 33 32 30 30 29 28 27 26? 24)
[*] SC: 30 (33 33 31 30)
[*] IA: 29 (33 30 31 29 29 29 29 29 29 29 29 29) *
[*] NE: 28 (34 30 28 28 27 27 26 26 25 25)
[*] SD: 22 (30 29 24 22 22 22 21 21 20 20)
[/list]
Cutoffs Unknown

* means that CDR is official in that state.

Notes

For those asking about the removal of the tiers, I'd like to quote Jason himself:
[quote=peace09]
learn from my mistakes
[/quote]

Help contribute by sharing your state's cutoffs!
569 replies
SirAppel
Apr 1, 2025
ethan2011
2 minutes ago
Some problems
hashbrown2009   1
N 17 minutes ago by SpeedCuber7
1. Real numbers a,b,c are satisfy a+1/b = b+1/c = c+1/a =x. If a,b,c are distinct, what is the value of x?
2. If x^2+y^2=1, then what is the value of : root(x^2-2x+1) + root(xy-2x+y-2) ?
3. Find the value of the sequence 2^2 + (3^2+1) + (4^2+2) + … + (97^2+95) + (98^2+96).
4. If x^2+x-1=0, then evaluate (1-x^2-x^3-x^4-…-x^2022-x^2023)/x^2022 .
5. If triangle XYZ has 3 sides that are all whole numbers, and the perimeter of XYZ is 24, what is the probability XYZ is a right triangle?

Note: If someone can latex-ify this it would help.
1 reply
2 viewing
hashbrown2009
20 minutes ago
SpeedCuber7
17 minutes ago
9 What is the most important topic in maths competition?
AVIKRIS   20
N an hour ago by Yiyj1
I think arithmetic is the most the most important topic in math competitions.
20 replies
AVIKRIS
6 hours ago
Yiyj1
an hour ago
"Median" Geo
asbodke   25
N an hour ago by Giant_PT
Source: 2023 USA TSTST Problem 1
Let $ABC$ be a triangle with centroid $G$. Points $R$ and $S$ are chosen on rays $GB$ and $GC$, respectively, such that
\[ \angle ABS=\angle ACR=180^\circ-\angle BGC.\]Prove that $\angle RAS+\angle BAC=\angle BGC$.

Merlijn Staps
25 replies
asbodke
Jun 26, 2023
Giant_PT
an hour ago
Find all positive integers a and b
orl   4
N an hour ago by Assassino9931
Source: IMO Shortlist 1996, N4
Find all positive integers $ a$ and $ b$ for which

\[ \left \lfloor \frac{a^2}{b} \right \rfloor + \left \lfloor \frac{b^2}{a} \right \rfloor = \left \lfloor \frac{a^2 + b^2}{ab} \right \rfloor + ab.\]
4 replies
orl
Aug 9, 2008
Assassino9931
an hour ago
2500th post
Solocraftsolo   20
N an hour ago by K1mchi_
i keep forgetting to do these...


2500 is cool.

i am not very sentimental so im not going to post a math story or anything.

here are some problems though

p1p2p3

p4
20 replies
1 viewing
Solocraftsolo
Apr 16, 2025
K1mchi_
an hour ago
PX, IO, MN, BC concurrent iff sides of ABC form arithmetic prgression
parmenides51   2
N an hour ago by ihategeo_1969
Source: 2019 Geo Mock - Olympiad by Tovi Wen #3 https://artofproblemsolving.com/community/c594864h1787237p11805928
Let $ABC$ be a triangle with $AB \le BC \le CA$, incenter $I$, circumcenter $O$, and circumcircle $\Gamma$. The line $\overline{AI}$ meets $\overline{BC}$ at $D$, and meets $\Gamma$ again at $M$. Let $N$ be the reflection of $M$ over $\overline{OD}$. Let the line through $N$ perpendicular to $\overline{BC}$ meet $\overline{AI}$ at $P$. $\overline{IO}$ meets $\overline{AB}$ and $\overline{AC}$ at $E$ and $F$, respectively. Suppose that the circumcircle of $\triangle{AEF}$ meets $\Gamma$ again at $X$. Prove that $\overline{PX}$, $\overline{IO}$, $\overline{MN}$, $\overline{BC}$ are concurrent if and only if the sides of $\triangle{ABC}$ form an arithmetic progression.
2 replies
parmenides51
Nov 26, 2023
ihategeo_1969
an hour ago
Functional Equation
anantmudgal09   20
N 2 hours ago by bin_sherlo
Source: India TST 2018 D1 P3
Find all functions $f: \mathbb{R} \mapsto \mathbb{R}$ such that $$f(x)f\left(yf(x)-1\right)=x^2f(y)-f(x),$$for all $x,y \in \mathbb{R}$.
20 replies
anantmudgal09
Jul 18, 2018
bin_sherlo
2 hours ago
Killer NT that nobody solved (also my hardest NT ever created)
mshtand1   0
2 hours ago
Source: Ukraine IMO 2025 TST P8
A positive integer number \( a \) is chosen. Prove that there exists a prime number that divides infinitely many terms of the sequence \( \{b_k\}_{k=1}^{\infty} \), where
\[
b_k = a^{k^k} \cdot 2^{2^k - k} + 1.
\]
Proposed by Arsenii Nikolaev and Mykhailo Shtandenko
0 replies
mshtand1
2 hours ago
0 replies
Squares on height in right triangle
Miquel-point   0
3 hours ago
Source: Romanian NMO 2025 7.4
Consider the right-angled triangle $ABC$ with $\angle A$ right and $AD\perp BC$, $D\in BC$. On the ray $[AD$ we take two points $E$ and $H$ so that $AE=AC$ and $AH=AB$. Consider the squares $AEFG$ and $AHJI$ containing inside $C$ and $B$, respectively. If $K=EG\cap AC$ and $L=IH\cap AB$, $N=IL\cap GK$ and $M=IB\cap GC$, prove that $LK\parallel BC$ and that $A$, $N$ and $M$ are collinear.
0 replies
Miquel-point
3 hours ago
0 replies
Projections on lateral faces of pyramid are coplanar
Miquel-point   0
3 hours ago
Source: Romanian NMO 2025 8.4
From a point $O$ inside a square $ABCD$ we raise a segment $OS$ perpendicular to the plane of the square. Show that the projections of $O$ on the planes $(SAB)$, $(SBC)$, $(SCD)$ and $(SDA)$ are coplanar if and only if $O\in [AC]\cup [BD]$.
0 replies
Miquel-point
3 hours ago
0 replies
NT equation
EthanWYX2009   3
N 3 hours ago by pavel kozlov
Source: 2025 TST T11
Let \( n \geq 4 \). Proof that
\[
(2^x - 1)(5^x - 1) = y^n
\]have no positive integer solution \((x, y)\).
3 replies
EthanWYX2009
Mar 10, 2025
pavel kozlov
3 hours ago
math olympiads
Lirimath   1
N 3 hours ago by maromex
Let a,b,c be real numbers such that a^2(b+c)+b^2(c+a)+c^2(a+b)=3(a+b+c-1) and a+b+c differnet by 0.Prove that ab+bc+ca=3 if and only if abc=1
1 reply
Lirimath
4 hours ago
maromex
3 hours ago
math olympiad
Lirimath   2
N 4 hours ago by maromex
Let a,b,c be positive real numbers such that a+b+c=3abc.Prove that
a^2+b^2+c^2+3>=2(ab+bc+ca).
2 replies
Lirimath
4 hours ago
maromex
4 hours ago
Annoying Probability Math Problem
RYang2   13
N Yesterday at 2:00 AM by FabulousSpider24
I was working in my math textbook(not the AoPS one) when I came across this math problem:

Determine if the events are dependent or independent.
1. Drawing a red and a blue marble at the same time from a bag containing 6 red and 4 blue marbles
2.(omitted)

I thought it was independent, since the events happen at the same time, but the textbook answer said dependent.
Can someone help me understand(or prove the textbook wrong)?
13 replies
RYang2
Mar 14, 2018
FabulousSpider24
Yesterday at 2:00 AM
Annoying Probability Math Problem
G H J
G H BBookmark kLocked kLocked NReply
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RYang2
1936 posts
#1 • 2 Y
Y by Adventure10, Mango247
I was working in my math textbook(not the AoPS one) when I came across this math problem:

Determine if the events are dependent or independent.
1. Drawing a red and a blue marble at the same time from a bag containing 6 red and 4 blue marbles
2.(omitted)

I thought it was independent, since the events happen at the same time, but the textbook answer said dependent.
Can someone help me understand(or prove the textbook wrong)?
This post has been edited 1 time. Last edited by RYang2, Mar 14, 2018, 5:10 PM
Reason: Too general subject
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math_is_life_2004
1397 posts
#2 • 1 Y
Y by Adventure10
It’s dependent
Z K Y
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RYang2
1936 posts
#3 • 1 Y
Y by Adventure10
Explain?
Z K Y
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math_is_life_2004
1397 posts
#4 • 2 Y
Y by Adventure10, Mango247
Actually I think its independent what grade textbook you have?
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brainpopper
1052 posts
#5 • 2 Y
Y by Adventure10, Mango247
Independent is only when they are replace or when the probability doesn't change, right? In #1, If we draw a blue marble first, the probability is 6/10 but the next red marble is 4/9
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RYang2
1936 posts
#6 • 2 Y
Y by Adventure10, Mango247
Pre-Algebra Textbook
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RYang2
1936 posts
#7 • 2 Y
Y by Adventure10, Mango247
And, the problem said at the same time, so there would be no "first" or "second"
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math_is_life_2004
1397 posts
#8 • 2 Y
Y by Adventure10, Mango247
RYang2 wrote:
Pre-Algebra Textbook

Oh I haven’t done that for 2 years. After you memorized the law of cosine you kinda forget everything. #2ndquadraticequation
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creeperhissboom
224 posts
#9 • 2 Y
Y by Adventure10, Mango247
It is dependant.

It is the same as taking one out at a time.
It is only independant if there is replacement.
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A-Username
70 posts
#10 • 2 Y
Y by Adventure10, Mango247
RYang2 wrote:
I was working in my math textbook(not the AoPS one) when I came across this math problem:

Determine if the events are dependent or independent.
1. Drawing a red and a blue marble at the same time from a bag containing 6 red and 4 blue marbles
2.(omitted)

I thought it was independent, since the events happen at the same time, but the textbook answer said dependent.
Can someone help me understand(or prove the textbook wrong)?

@RYang2 Easy explanation for #1 is
Independent-Event 1 doesn't influence Event 2.
Dependent-Event 1 does influence Event 2.
Since this bag contains 6 red and 4 blues, there are 10 marbles in the bag. Now, we know that the color doesn't really matter because we know there is more than 1 for each color. Then we can determine which definition it fits better. First, we know it can't be dependent because if we take it at the same time, there is no sense of order and that the taking of the blue doesn't affect the number of reds there are and vice versa.
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EthanNg6
13 posts
#11
Y by
It's probably dependent
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Jaxman8
113 posts
#12
Y by
I think dependent, if you were to calculate the probabilities for blue first vs red first it’s the same
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giratina3
494 posts
#13 • 1 Y
Y by EthanNg6
The answer is dependent. When you pick 2 marbles, the first pick affects the second one. Although you pick the two at the same time, the change in marble just occurs instantly, so it is still dependent (most average school textbook problem)
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FabulousSpider24
69 posts
#14 • 1 Y
Y by EthanNg6
You can think about it like this: It is dependent because as soon as the first marble is taken, the number of marbles in the bag decreases and so the probability of picking a marble (either red or blue) will change immediately afterwards. .
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