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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
Triangular Numbers in action
integrated_JRC   28
N a few seconds ago by SomeonecoolLovesMaths
Source: RMO 2018 P5
Find all natural numbers $n$ such that $1+[\sqrt{2n}]~$ divides $2n$.

( For any real number $x$ , $[x]$ denotes the largest integer not exceeding $x$. )
28 replies
integrated_JRC
Oct 7, 2018
SomeonecoolLovesMaths
a few seconds ago
another n x n table problem.
pohoatza   3
N 11 minutes ago by reni_wee
Source: Romanian JBTST III 2007, problem 3
Consider a $n$x$n$ table such that the unit squares are colored arbitrary in black and white, such that exactly three of the squares placed in the corners of the table are white, and the other one is black. Prove that there exists a $2$x$2$ square which contains an odd number of unit squares white colored.
3 replies
pohoatza
May 13, 2007
reni_wee
11 minutes ago
Concurrency from isogonal Mittenpunkt configuration
MarkBcc168   18
N 11 minutes ago by ihategeo_1969
Source: Fake USAMO 2020 P3
Let $\triangle ABC$ be a scalene triangle with circumcenter $O$, incenter $I$, and incircle $\omega$. Let $\omega$ touch the sides $\overline{BC}$, $\overline{CA}$, and $\overline{AB}$ at points $D$, $E$, and $F$ respectively. Let $T$ be the projection of $D$ to $\overline{EF}$. The line $AT$ intersects the circumcircle of $\triangle ABC$ again at point $X\ne A$. The circumcircles of $\triangle AEX$ and $\triangle AFX$ intersect $\omega$ again at points $P\ne E$ and $Q\ne F$ respectively. Prove that the lines $EQ$, $FP$, and $OI$ are concurrent.

Proposed by MarkBcc168.
18 replies
MarkBcc168
Apr 28, 2020
ihategeo_1969
11 minutes ago
Anything real in this system must be integer
Assassino9931   8
N 21 minutes ago by Abdulaziz_Radjabov
Source: Al-Khwarizmi International Junior Olympiad 2025 P1
Determine the largest integer $c$ for which the following statement holds: there exists at least one triple $(x,y,z)$ of integers such that
\begin{align*} x^2 + 4(y + z) = y^2 + 4(z + x) = z^2 + 4(x + y) = c \end{align*}and all triples $(x,y,z)$ of real numbers, satisfying the equations, are such that $x,y,z$ are integers.

Marek Maruin, Slovakia
8 replies
Assassino9931
May 9, 2025
Abdulaziz_Radjabov
21 minutes ago
Inequalities
sqing   7
N 5 hours ago by sqing
Let $ a,b,c>0 , a+b+c +abc=4$. Prove that
$$ \frac {a}{a^2+2}+\frac {b}{b^2+2}+\frac {c}{c^2+2} \leq 1$$Let $ a,b,c>0 , ab+bc+ca+abc=4$. Prove that
$$ \frac {a}{a^2+2}+\frac {b}{b^2+2}+\frac {c}{c^2+2} \leq 1$$
7 replies
sqing
Yesterday at 12:28 PM
sqing
5 hours ago
2024 Mock AIME 1 ** p15 (cheaters' trap) - 128 | n^{\sigma (n)} - \sigma(n^n)
parmenides51   5
N 5 hours ago by Amkan2022
Let $N$ be the number of positive integers $n$ such that $n$ divides $2024^{2024}$ and $128$ divides
$$n^{\sigma (n)} - \sigma(n^n)$$where $\sigma (n)$ denotes the number of positive integers that divide $n$, including $1$ and $n$. Find the remainder when $N$ is divided by $1000$.
5 replies
parmenides51
Jan 29, 2025
Amkan2022
5 hours ago
If $a\cos A+b\sin A=m,$ and $a\sin A-b\cos A=n,$ then find the value of $a^2 +b^
Vulch   1
N Today at 9:22 AM by Captainscrubz
If $a\cos A+b\sin A=m,$ and $a\sin A-b\cos A=n,$ then find the value of $a^2 +b^2.$
1 reply
Vulch
Today at 7:54 AM
Captainscrubz
Today at 9:22 AM
Inequalities
sqing   8
N Today at 2:45 AM by sqing
Let $a,b,c >2 $ and $ ab+bc+ca \leq 75.$ Show that
$$\frac{1}{a-2}+\frac{1}{b-2}+\frac{1}{c-2}\geq 1$$Let $a,b,c >2 $ and $ \frac{1}{a}+\frac{1}{b}+\frac{1}{c}\geq \frac{6}{7}.$ Show that
$$\frac{1}{a-2}+\frac{1}{b-2}+\frac{1}{c-2}\geq 2$$
8 replies
sqing
May 13, 2025
sqing
Today at 2:45 AM
trigonometric functions
VivaanKam   16
N Today at 1:03 AM by Shan3t
Hi could someone explain the basic trigonometric functions to me like sin, cos, tan etc.
Thank you!
16 replies
VivaanKam
Apr 29, 2025
Shan3t
Today at 1:03 AM
Weird locus problem
Sedro   7
N Yesterday at 8:00 PM by ReticulatedPython
Points $A$ and $B$ are in the coordinate plane such that $AB=2$. Let $\mathcal{H}$ denote the locus of all points $P$ in the coordinate plane satisfying $PA\cdot PB=2$, and let $M$ be the midpoint of $AB$. Points $X$ and $Y$ are on $\mathcal{H}$ such that $\angle XMY = 45^\circ$ and $MX\cdot MY=\sqrt{2}$. The value of $MX^4 + MY^4$ can be expressed in the form $\tfrac{m}{n}$, where $m$ and $n$ are relatively prime positive integers. Find $m+n$.
7 replies
Sedro
May 11, 2025
ReticulatedPython
Yesterday at 8:00 PM
IOQM P23 2024
SomeonecoolLovesMaths   3
N Yesterday at 4:53 PM by lakshya2009
Consider the fourteen numbers, $1^4,2^4,...,14^4$. The smallest natural numebr $n$ such that they leave distinct remainders when divided by $n$ is:
3 replies
SomeonecoolLovesMaths
Sep 8, 2024
lakshya2009
Yesterday at 4:53 PM
Inequalities
sqing   2
N Yesterday at 4:05 PM by MITDragon
Let $ 0\leq x,y,z\leq 2. $ Prove that
$$-48\leq (x-yz)( 3y-zx)(z-xy)\leq 9$$$$-144\leq (3x-yz)(y-zx)(3z-xy)\leq\frac{81}{64}$$$$-144\leq (3x-yz)(2y-zx)(3z-xy)\leq\frac{81}{16}$$
2 replies
sqing
May 9, 2025
MITDragon
Yesterday at 4:05 PM
Pells equation
Entrepreneur   0
Yesterday at 3:56 PM
A Pells Equation is defined as follows $$x^2-1=ky^2.$$Where $x,y$ are positive integers and $k$ is a non-square positive integer. If $(x_n,y_n)$ denotes the n-th set of solution to the equation with $(x_0,y_0)=(1,0).$ Then, prove that $$x_{n+1}x_n-ky_{n+1}y_n=x_1,$$$$x_n\pm y_n\sqrt k=(x_1\pm y_1\sqrt k)^n.$$
0 replies
Entrepreneur
Yesterday at 3:56 PM
0 replies
Incircle concurrency
niwobin   1
N Yesterday at 2:42 PM by niwobin
Triangle ABC with incenter I, incircle is tangent to BC, AC, and AB at D, E and F respectively.
DT is a diameter for the incircle, and AT meets the incircle again at point H.
Let DH and EF intersect at point J. Prove: AJ//BC.
1 reply
niwobin
May 11, 2025
niwobin
Yesterday at 2:42 PM
d | \overline{aabbcc} iff d | \overline{abc} where d is two digit number
parmenides51   1
N Apr 29, 2025 by luphuc
Source: Czech-Polish-Slovak Junior Match 2013, Individual p4 CPSJ
Determine the largest two-digit number $d$ with the following property:
for any six-digit number $\overline{aabbcc}$ number $d$ is a divisor of the number $\overline{aabbcc}$ if and only if the number $d$ is a divisor of the corresponding three-digit number $\overline{abc}$.

Note The numbers $a \ne 0, b$ and $c$ need not be different.
1 reply
parmenides51
Mar 14, 2020
luphuc
Apr 29, 2025
d | \overline{aabbcc} iff d | \overline{abc} where d is two digit number
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G H BBookmark kLocked kLocked NReply
Source: Czech-Polish-Slovak Junior Match 2013, Individual p4 CPSJ
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parmenides51
30652 posts
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Determine the largest two-digit number $d$ with the following property:
for any six-digit number $\overline{aabbcc}$ number $d$ is a divisor of the number $\overline{aabbcc}$ if and only if the number $d$ is a divisor of the corresponding three-digit number $\overline{abc}$.

Note The numbers $a \ne 0, b$ and $c$ need not be different.
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luphuc
23 posts
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Do you have answer ?
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