Stay ahead of learning milestones! Enroll in a class over the summer!

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k a April Highlights and 2025 AoPS Online Class Information
jlacosta   0
Wednesday at 3:18 PM
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]
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All classes run 7:30pm-8:45pm ET/4:30pm - 5:45pm PT unless otherwise noted.

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0 replies
jlacosta
Wednesday at 3:18 PM
0 replies
A board with crosses that we color
nAalniaOMliO   1
N 18 minutes ago by EmersonSoriano
Source: Belarusian National Olympiad 2025
In some cells of the table $2025 \times 2025$ crosses are placed. A set of 2025 cells we will call balanced if no two of them are in the same row or column. It is known that any balanced set has at least $k$ crosses.
Find the minimal $k$ for which it is always possible to color crosses in two colors such that any balanced set has crosses of both colors.
1 reply
nAalniaOMliO
Mar 28, 2025
EmersonSoriano
18 minutes ago
Inspired by JK1603JK
sqing   1
N 36 minutes ago by Soupboy0
Source: Own
Let $ a,b,c\geq 0 $ and $ab+bc+ca=1.$ Prove that$$\frac{abc-2}{abc-1}\ge \frac{4(a^2b+b^2c+c^2a)}{a^3b+b^3c+c^3a+1} $$$$\frac{abc-1}{abc-2}\ge \frac{(\sqrt 2-1)(a^2b+b^2c+c^2a+1)}{a^3b+b^3c+c^3a+1} $$
1 reply
1 viewing
sqing
42 minutes ago
Soupboy0
36 minutes ago
Olympiad Geometry problem-second time posting
kjhgyuio   7
N an hour ago by kjhgyuio
Source: smo problem
In trapezium ABCD,AD is parallel to BC and points E and F are midpoints of AB and DC respectively. If
Area of AEFD/Area of EBCF =√3 + 1/3-√3 and the area of triangle ABD is √3 .find the area of trapezium ABCD
7 replies
kjhgyuio
Apr 2, 2025
kjhgyuio
an hour ago
series and factorials?
jenishmalla   5
N an hour ago by Tony_stark0094
Source: 2025 Nepal ptst p4 of 4
Find all pairs of positive integers \( n \) and \( x \) such that
\[
1^n + 2^n + 3^n + \cdots + n^n = x!
\]
(Petko Lazarov, Bulgaria)
5 replies
jenishmalla
Mar 15, 2025
Tony_stark0094
an hour ago
No more topics!
Monkeys have bananas
nAalniaOMliO   5
N Mar 30, 2025 by jkim0656
Source: Belarusian National Olympiad 2025
Ten monkeys have 60 bananas. Each monkey has at least one banana and any two monkeys have different amounts of bananas.
Prove that any six monkeys can distribute their bananas between others such that all 4 remaining monkeys have the same amount of bananas.
5 replies
nAalniaOMliO
Mar 28, 2025
jkim0656
Mar 30, 2025
Monkeys have bananas
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G H BBookmark kLocked kLocked NReply
Source: Belarusian National Olympiad 2025
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nAalniaOMliO
294 posts
#1
Y by
Ten monkeys have 60 bananas. Each monkey has at least one banana and any two monkeys have different amounts of bananas.
Prove that any six monkeys can distribute their bananas between others such that all 4 remaining monkeys have the same amount of bananas.
Z K Y
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RagvaloD
4894 posts
#2
Y by
$9$ monkeys can have at least $1+2+...+9=45$ bananas, so one monkey can not have more than $15$ bananas
And so for any $4$ monkeys it is possible to distribute all remaining bananas, so every monkey will have $15$ bananas
Z K Y
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nAalniaOMIiO
2 posts
#3
Y by
Fairly easy problem.
Z K Y
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jkim0656
530 posts
#4
Y by
why is this under HSO
also how is this a nat oly???
This post has been edited 1 time. Last edited by jkim0656, Mar 29, 2025, 11:36 PM
Z K Y
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nAalniaOMliO
294 posts
#5
Y by
jkim0656 wrote:
why is this under HSO
also how is this a nat oly???
That's the first problem in the lowest grade on the olympiad. Check out the second problem in the same test, you might find it not obvious.
It is under HSO because it was on a HSO. Or where should I post it?
This post has been edited 1 time. Last edited by nAalniaOMliO, Mar 30, 2025, 9:13 AM
Z K Y
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jkim0656
530 posts
#6
Y by
sryy mb :blush:
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