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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
9 Fun Proof Endings
elasticwealth   33
N a minute ago by cheltstudent
It seems like AOPS is going through a stressful phase right now.

Let's lighten the mood by voting on the best proof endings!
33 replies
elasticwealth
Today at 12:26 AM
cheltstudent
a minute ago
USA(J)MO Statistics Out
BS2012   34
N 2 minutes ago by lpieleanu
Source: MAA edvistas page
https://maa.edvistas.com/eduview/report.aspx?view=1561&mode=6
who were the 2 usamo perfects
34 replies
BS2012
Yesterday at 10:07 PM
lpieleanu
2 minutes ago
I got the horses in the BAC
fidgetboss_4000   49
N 8 minutes ago by lpieleanu
Source: 2021 AIME II #14
Let $\triangle ABC$ be an acute triangle with circumcenter $O$ and centroid $G$. Let $X$ be the intersection of the line tangent to the circumcircle of $\triangle ABC$ at $A$ and the line perpendicular to $GO$ at $G$. Let $Y$ be the intersection of lines $XG$ and $BC$. Given that the measures of $\angle ABC, \angle BCA, $ and $\angle XOY$ are in the ratio $13 : 2 : 17, $ the degree measure of $\angle BAC$ can be written as $\frac{m}{n},$ where $m$ and $n$ are relatively prime positive integers. Find $m+n$.
IMAGE
49 replies
fidgetboss_4000
Mar 19, 2021
lpieleanu
8 minutes ago
2025 USAMO Rubric
plang2008   24
N 43 minutes ago by Mathdreams
1. Let $k$ and $d$ be positive integers. Prove that there exists a positive integer $N$ such that for every odd integer $n>N$, the digits in the base-$2n$ representation of $n^k$ are all greater than $d$.

Rubric for Problem 1

2. Let $n$ and $k$ be positive integers with $k<n$. Let $P(x)$ be a polynomial of degree $n$ with real coefficients, nonzero constant term, and no repeated roots. Suppose that for any real numbers $a_0,\,a_1,\,\ldots,\,a_k$ such that the polynomial $a_kx^k+\cdots+a_1x+a_0$ divides $P(x)$, the product $a_0a_1\cdots a_k$ is zero. Prove that $P(x)$ has a nonreal root.

Rubric for Problem 2

3. Alice the architect and Bob the builder play a game. First, Alice chooses two points $P$ and $Q$ in the plane and a subset $\mathcal{S}$ of the plane, which are announced to Bob. Next, Bob marks infinitely many points in the plane, designating each a city. He may not place two cities within distance at most one unit of each other, and no three cities he places may be collinear. Finally, roads are constructed between the cities as follows: for each pair $A,\,B$ of cities, they are connected with a road along the line segment $AB$ if and only if the following condition holds:
[center]For every city $C$ distinct from $A$ and $B$, there exists $R\in\mathcal{S}$ such[/center]
[center]that $\triangle PQR$ is directly similar to either $\triangle ABC$ or $\triangle BAC$.[/center]
Alice wins the game if (i) the resulting roads allow for travel between any pair of cities via a finite sequence of roads and (ii) no two roads cross. Otherwise, Bob wins. Determine, with proof, which player has a winning strategy.

Note: $\triangle UVW$ is directly similar to $\triangle XYZ$ if there exists a sequence of rotations, translations, and dilations sending $U$ to $X$, $V$ to $Y$, and $W$ to $Z$.

Rubric for Problem 3

4. Let $H$ be the orthocenter of acute triangle $ABC$, let $F$ be the foot of the altitude from $C$ to $AB$, and let $P$ be the reflection of $H$ across $BC$. Suppose that the circumcircle of triangle $AFP$ intersects line $BC$ at two distinct points $X$ and $Y$. Prove that $C$ is the midpoint of $XY$.

Rubric for Problem 4

5. Determine, with proof, all positive integers $k$ such that \[\frac{1}{n+1} \sum_{i=0}^n \binom{n}{i}^k\]is an integer for every positive integer $n$.

Rubric for Problem 5

6. Let $m$ and $n$ be positive integers with $m\geq n$. There are $m$ cupcakes of different flavors arranged around a circle and $n$ people who like cupcakes. Each person assigns a nonnegative real number score to each cupcake, depending on how much they like the cupcake. Suppose that for each person $P$, it is possible to partition the circle of $m$ cupcakes into $n$ groups of consecutive cupcakes so that the sum of $P$'s scores of the cupcakes in each group is at least $1$. Prove that it is possible to distribute the $m$ cupcakes to the $n$ people so that each person $P$ receives cupcakes of total score at least $1$ with respect to $P$.

Rubric for Problem 6
24 replies
plang2008
Apr 2, 2025
Mathdreams
43 minutes ago
No more topics!
JMPSC Year 3 Problems/Results/Statistics
samrocksnature   3
N Aug 20, 2023 by samrocksnature
Hey everyone!

Thank you to all who participated in the third year of JMPSC. The solutions, statistics, and problems are linked to this post, and the top 20 of each division can be found here.

Enjoy the problems!

3 replies
samrocksnature
Aug 19, 2023
samrocksnature
Aug 20, 2023
JMPSC Year 3 Problems/Results/Statistics
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samrocksnature
8791 posts
#1 • 6 Y
Y by aidan0626, kante314, Math4Life7, KevinYang2.71, SouradipClash_03, Danielzh
Hey everyone!

Thank you to all who participated in the third year of JMPSC. The solutions, statistics, and problems are linked to this post, and the top 20 of each division can be found here.

Enjoy the problems!
Attachments:
JMPSC3Stats.pdf (91kb)
JMPSC3Solutions.pdf (523kb)
JMPSC3Problems.pdf (445kb)
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Math4Life7
1703 posts
#3
Y by
I am pretty sure that the solution to problem 12 d1r2 has a typo
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palindrome868
1175 posts
#4
Y by
imma check the sol for that problem soon
this message will be edited when i do so

uh, i don't see a typo, the solution seems good to me?
This post has been edited 1 time. Last edited by palindrome868, Aug 20, 2023, 2:09 AM
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samrocksnature
8791 posts
#5 • 2 Y
Y by aie8920, MathFan335
Math4Life7 wrote:
I am pretty sure that the solution to problem 12 d1r2 has a typo

Thank you Jacob for writing all the solutions!
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