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Middle School Math
Grades 5-8, Ages 10-13, MATHCOUNTS, AMC 8
Grades 5-8, Ages 10-13, MATHCOUNTS, AMC 8
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Middle School Math
Grades 5-8, Ages 10-13, MATHCOUNTS, AMC 8
Grades 5-8, Ages 10-13, MATHCOUNTS, AMC 8
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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.
Introductory: Grades 5-10
Prealgebra 1 Self-Paced
Prealgebra 1
Tuesday, May 13 - Aug 26
Thursday, May 29 - Sep 11
Sunday, Jun 15 - Oct 12
Monday, Jun 30 - Oct 20
Wednesday, Jul 16 - Oct 29
Prealgebra 2 Self-Paced
Prealgebra 2
Wednesday, May 7 - Aug 20
Monday, Jun 2 - Sep 22
Sunday, Jun 29 - Oct 26
Friday, Jul 25 - Nov 21
Introduction to Algebra A Self-Paced
Introduction to Algebra A
Sunday, May 11 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Wednesday, May 14 - Aug 27
Friday, May 30 - Sep 26
Monday, Jun 2 - Sep 22
Sunday, Jun 15 - Oct 12
Thursday, Jun 26 - Oct 9
Tuesday, Jul 15 - Oct 28
Introduction to Counting & Probability Self-Paced
Introduction to Counting & Probability
Thursday, May 15 - Jul 31
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Wednesday, Jul 9 - Sep 24
Sunday, Jul 27 - Oct 19
Introduction to Number Theory
Friday, May 9 - Aug 1
Wednesday, May 21 - Aug 6
Monday, Jun 9 - Aug 25
Sunday, Jun 15 - Sep 14
Tuesday, Jul 15 - Sep 30
Introduction to Algebra B Self-Paced
Introduction to Algebra B
Tuesday, May 6 - Aug 19
Wednesday, Jun 4 - Sep 17
Sunday, Jun 22 - Oct 19
Friday, Jul 18 - Nov 14
Introduction to Geometry
Sunday, May 11 - Nov 9
Tuesday, May 20 - Oct 28
Monday, Jun 16 - Dec 8
Friday, Jun 20 - Jan 9
Sunday, Jun 29 - Jan 11
Monday, Jul 14 - Jan 19
Paradoxes and Infinity
Mon, Tue, Wed, & Thurs, Jul 14 - Jul 16 (meets every day of the week!)
Intermediate: Grades 8-12
Intermediate Algebra
Sunday, Jun 1 - Nov 23
Tuesday, Jun 10 - Nov 18
Wednesday, Jun 25 - Dec 10
Sunday, Jul 13 - Jan 18
Thursday, Jul 24 - Jan 22
Intermediate Counting & Probability
Wednesday, May 21 - Sep 17
Sunday, Jun 22 - Nov 2
Intermediate Number Theory
Sunday, Jun 1 - Aug 24
Wednesday, Jun 18 - Sep 3
Precalculus
Friday, May 16 - Oct 24
Sunday, Jun 1 - Nov 9
Monday, Jun 30 - Dec 8
Advanced: Grades 9-12
Olympiad Geometry
Tuesday, Jun 10 - Aug 26
Calculus
Tuesday, May 27 - Nov 11
Wednesday, Jun 25 - Dec 17
Group Theory
Thursday, Jun 12 - Sep 11
Contest Preparation: Grades 6-12
MATHCOUNTS/AMC 8 Basics
Friday, May 23 - Aug 15
Monday, Jun 2 - Aug 18
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
MATHCOUNTS/AMC 8 Advanced
Sunday, May 11 - Aug 10
Tuesday, May 27 - Aug 12
Wednesday, Jun 11 - Aug 27
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
AMC 10 Problem Series
Friday, May 9 - Aug 1
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Tuesday, Jun 17 - Sep 2
Sunday, Jun 22 - Sep 21 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Monday, Jun 23 - Sep 15
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
AMC 10 Final Fives
Sunday, May 11 - Jun 8
Tuesday, May 27 - Jun 17
Monday, Jun 30 - Jul 21
AMC 12 Problem Series
Tuesday, May 27 - Aug 12
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Wednesday, Aug 6 - Oct 22
AMC 12 Final Fives
Sunday, May 18 - Jun 15
AIME Problem Series A
Thursday, May 22 - Jul 31
AIME Problem Series B
Sunday, Jun 22 - Sep 21
F=ma Problem Series
Wednesday, Jun 11 - Aug 27
WOOT Programs
Visit the pages linked for full schedule details for each of these programs!
MathWOOT Level 1
MathWOOT Level 2
ChemWOOT
CodeWOOT
PhysicsWOOT
Programming
Introduction to Programming with Python
Thursday, May 22 - Aug 7
Sunday, Jun 15 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Tuesday, Jun 17 - Sep 2
Monday, Jun 30 - Sep 22
Intermediate Programming with Python
Sunday, Jun 1 - Aug 24
Monday, Jun 30 - Sep 22
USACO Bronze Problem Series
Tuesday, May 13 - Jul 29
Sunday, Jun 22 - Sep 1
Physics
Introduction to Physics
Wednesday, May 21 - Aug 6
Sunday, Jun 15 - Sep 14
Monday, Jun 23 - Sep 15
Physics 1: Mechanics
Thursday, May 22 - Oct 30
Monday, Jun 23 - Dec 15
Relativity
Mon, Tue, Wed & Thurs, Jun 23 - Jun 26 (meets every day of the week!)
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.
Introductory: Grades 5-10
Prealgebra 1 Self-Paced
Prealgebra 1
Tuesday, May 13 - Aug 26
Thursday, May 29 - Sep 11
Sunday, Jun 15 - Oct 12
Monday, Jun 30 - Oct 20
Wednesday, Jul 16 - Oct 29
Prealgebra 2 Self-Paced
Prealgebra 2
Wednesday, May 7 - Aug 20
Monday, Jun 2 - Sep 22
Sunday, Jun 29 - Oct 26
Friday, Jul 25 - Nov 21
Introduction to Algebra A Self-Paced
Introduction to Algebra A
Sunday, May 11 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Wednesday, May 14 - Aug 27
Friday, May 30 - Sep 26
Monday, Jun 2 - Sep 22
Sunday, Jun 15 - Oct 12
Thursday, Jun 26 - Oct 9
Tuesday, Jul 15 - Oct 28
Introduction to Counting & Probability Self-Paced
Introduction to Counting & Probability
Thursday, May 15 - Jul 31
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Wednesday, Jul 9 - Sep 24
Sunday, Jul 27 - Oct 19
Introduction to Number Theory
Friday, May 9 - Aug 1
Wednesday, May 21 - Aug 6
Monday, Jun 9 - Aug 25
Sunday, Jun 15 - Sep 14
Tuesday, Jul 15 - Sep 30
Introduction to Algebra B Self-Paced
Introduction to Algebra B
Tuesday, May 6 - Aug 19
Wednesday, Jun 4 - Sep 17
Sunday, Jun 22 - Oct 19
Friday, Jul 18 - Nov 14
Introduction to Geometry
Sunday, May 11 - Nov 9
Tuesday, May 20 - Oct 28
Monday, Jun 16 - Dec 8
Friday, Jun 20 - Jan 9
Sunday, Jun 29 - Jan 11
Monday, Jul 14 - Jan 19
Paradoxes and Infinity
Mon, Tue, Wed, & Thurs, Jul 14 - Jul 16 (meets every day of the week!)
Intermediate: Grades 8-12
Intermediate Algebra
Sunday, Jun 1 - Nov 23
Tuesday, Jun 10 - Nov 18
Wednesday, Jun 25 - Dec 10
Sunday, Jul 13 - Jan 18
Thursday, Jul 24 - Jan 22
Intermediate Counting & Probability
Wednesday, May 21 - Sep 17
Sunday, Jun 22 - Nov 2
Intermediate Number Theory
Sunday, Jun 1 - Aug 24
Wednesday, Jun 18 - Sep 3
Precalculus
Friday, May 16 - Oct 24
Sunday, Jun 1 - Nov 9
Monday, Jun 30 - Dec 8
Advanced: Grades 9-12
Olympiad Geometry
Tuesday, Jun 10 - Aug 26
Calculus
Tuesday, May 27 - Nov 11
Wednesday, Jun 25 - Dec 17
Group Theory
Thursday, Jun 12 - Sep 11
Contest Preparation: Grades 6-12
MATHCOUNTS/AMC 8 Basics
Friday, May 23 - Aug 15
Monday, Jun 2 - Aug 18
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
MATHCOUNTS/AMC 8 Advanced
Sunday, May 11 - Aug 10
Tuesday, May 27 - Aug 12
Wednesday, Jun 11 - Aug 27
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
AMC 10 Problem Series
Friday, May 9 - Aug 1
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Tuesday, Jun 17 - Sep 2
Sunday, Jun 22 - Sep 21 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Monday, Jun 23 - Sep 15
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
AMC 10 Final Fives
Sunday, May 11 - Jun 8
Tuesday, May 27 - Jun 17
Monday, Jun 30 - Jul 21
AMC 12 Problem Series
Tuesday, May 27 - Aug 12
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Wednesday, Aug 6 - Oct 22
AMC 12 Final Fives
Sunday, May 18 - Jun 15
AIME Problem Series A
Thursday, May 22 - Jul 31
AIME Problem Series B
Sunday, Jun 22 - Sep 21
F=ma Problem Series
Wednesday, Jun 11 - Aug 27
WOOT Programs
Visit the pages linked for full schedule details for each of these programs!
MathWOOT Level 1
MathWOOT Level 2
ChemWOOT
CodeWOOT
PhysicsWOOT
Programming
Introduction to Programming with Python
Thursday, May 22 - Aug 7
Sunday, Jun 15 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Tuesday, Jun 17 - Sep 2
Monday, Jun 30 - Sep 22
Intermediate Programming with Python
Sunday, Jun 1 - Aug 24
Monday, Jun 30 - Sep 22
USACO Bronze Problem Series
Tuesday, May 13 - Jul 29
Sunday, Jun 22 - Sep 1
Physics
Introduction to Physics
Wednesday, May 21 - Aug 6
Sunday, Jun 15 - Sep 14
Monday, Jun 23 - Sep 15
Physics 1: Mechanics
Thursday, May 22 - Oct 30
Monday, Jun 23 - Dec 15
Relativity
Mon, Tue, Wed & Thurs, Jun 23 - Jun 26 (meets every day of the week!)
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
Find instructions and a list of contests to add here: https://artofproblemsolving.com/community/c40244h1064480_contests_to_add
1 reply
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]
[/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
, do not answer with "
is a solution" only. Either you post any kind of proof or at least something unexpected (like "
is the smallest solution). Someone that does not see that
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.
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]

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




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
sillies are bad
Bummer12345 6
N
11 minutes ago
by SpeedCuber7
I got 102nd and 89th place in 6th and 7th grade respectively; however, I feel like I definitely could've done much better (mainly due to sillies). For example, some of my worst sillies at nationals are
does anyone have tips to reduce silly mistakes (pls share, I really want to make top 56 this year)
2023 nats S1
2023 nats T5, 6, 7 (i don't even know how that happened)
2023 nats a team round question that would've allowed my state to get top 23
2024 nats 4ish sillies in the first 20ish problems of sprint
2023 nats T5, 6, 7 (i don't even know how that happened)
2023 nats a team round question that would've allowed my state to get top 23
2024 nats 4ish sillies in the first 20ish problems of sprint
does anyone have tips to reduce silly mistakes (pls share, I really want to make top 56 this year)
6 replies
Great similarity
steven_zhang123 3
N
17 minutes ago
by Lil_flip38
Source: a friend
As shown in the figure, there are two points
and
outside triangle
such that
and
. Connect
and
, which intersect at point
. Let
intersect
at point
. Prove that
.












3 replies
Geometry Help
ILOVECATS127 1
N
an hour ago
by Inaaya
Hello, I needed some help understanding this concept from Chapter 12, Geometry:
Points P, Q and R are on circle O such that
Arc PQ = 78°, arc QR = 123°, and arc PQR = 201°.
1. Find ∠PQO
2. Find ∠POR
Please help me understand HOW to solve these 2 problems.
Points P, Q and R are on circle O such that
Arc PQ = 78°, arc QR = 123°, and arc PQR = 201°.
1. Find ∠PQO
2. Find ∠POR
Please help me understand HOW to solve these 2 problems.
1 reply
AIME qualification
GallopingUnicorn45 8
N
an hour ago
by Inaaya
Hi, so I'm in 4th grade and I'm taking AMC 10 (both A and B) this year in November, and I really want to get AIME. Last time I did the 2023 AMC 10A was like four months ago (?) and I got 10 correct.
So I finished Intro to Counting and Number Theory and am almost done with Intro to Algebra B. Obviously there's some questions I don't know in those books, but I understand at least 90% of it.
I'm taking Intro to Geometry in the summer (it ends one week after AMC 10) and I'm just going to go over Intro to Algebra, Intro to Counting, and Intro to Number Theory (basically the questions I don't know and incorrect problems), plus Competition Math for Middle School and AoPS Volume 1: The Basics.
I will also do the past year AMC 10 papers, but is there anything else I can do to prepare and get into AIME? Thanks!
So I finished Intro to Counting and Number Theory and am almost done with Intro to Algebra B. Obviously there's some questions I don't know in those books, but I understand at least 90% of it.
I'm taking Intro to Geometry in the summer (it ends one week after AMC 10) and I'm just going to go over Intro to Algebra, Intro to Counting, and Intro to Number Theory (basically the questions I don't know and incorrect problems), plus Competition Math for Middle School and AoPS Volume 1: The Basics.
I will also do the past year AMC 10 papers, but is there anything else I can do to prepare and get into AIME? Thanks!
8 replies
AD=BE implies ABC right
v_Enhance 117
N
2 hours ago
by cj13609517288
Source: European Girl's MO 2013, Problem 1
The side
of the triangle
is extended beyond
to
so that
. The side
is extended beyond
to
so that
. Prove that, if
, then the triangle
is right-angled.











117 replies
Geometry
gggzul 6
N
3 hours ago
by Captainscrubz
In trapezoid
segments
and
are parallel. Angle bisectors of
and
meet at
. Angle bisectors of
and
meet at
. Prove that
is cyclic










6 replies
Geometry
Lukariman 5
N
3 hours ago
by Lukariman
Given circle (O) and point P outside (O). From P draw tangents PA and PB to (O) with contact points A, B. On the opposite ray of ray BP, take point M. The circle circumscribing triangle APM intersects (O) at the second point D. Let H be the projection of B on AM. Prove that
= 2∠AMP.

5 replies
Aime type Geo
ehuseyinyigit 4
N
5 hours ago
by ehuseyinyigit
Source: Turkish First Round 2024
In a scalene triangle
, let
be the midpoint of side
. Let the line perpendicular to
at point
intersect
at
. If
is tangent to
at
, find
.











4 replies

n variables with n-gon sides
mihaig 1
N
5 hours ago
by mihaig
Source: Own
Let
and let
be reals such that 
Prove



Prove

1 reply
Centroid, altitudes and medians, and concyclic points
BR1F1SZ 3
N
Today at 5:48 AM
by EeEeRUT
Source: Austria National MO Part 1 Problem 2
Let
be an acute triangle with
. Let
be the centroid of triangle
and let
be the foot of the perpendicular from
to side
. The median
intersects the circumcircle
of triangle
at a second point
. Let
be the point where
intersects
. The line
intersects the circle
at a point
, such that
lies between
and
. Prove that the points
and
lie on a circle.
(Karl Czakler)






















(Karl Czakler)
3 replies
area of O_1O_2O_3O_4 <=1, incenters of right triangles outside a square
parmenides51 2
N
Today at 4:35 AM
by Solilin
Source: Thailand Mathematical Olympiad 2012 p4
Let
be a unit square. Points
are chosen outside
so that
. Let
, respectively, be the incenters of
. Show that the area of
is at most
.








2 replies
Geo metry
TUAN2k8 3
N
Today at 4:34 AM
by TUAN2k8
Help me plss!
Given an acute triangle
. Points
and
lie on segments
and
, respectively. Lines
and
intersect at point
. The circumcircles of triangles
and
intersect at a second point
. The circumcircles of triangles
and
intersect at a second point
. Point
lies on segment
such that
. Prove that triangles
and
are similar.
Given an acute triangle



















3 replies

China South East Mathematical Olympiad 2013 problem 2
s372102 3
N
Today at 2:11 AM
by AGCN

























3 replies

State target p8 sol
G
H
J
G
H
BBookmark
kLocked
kLocked
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Y by PikaPika999
ikr i literally kinda guessed this one correct
This post has been edited 1 time. Last edited by greenplanet2050, Apr 6, 2025, 3:55 PM
Z
K
Y
The post below has been deleted. Click to close.
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Y by PikaPika999
greenplanet2050 wrote:
ikr i literally kinda guessed this one correct
Lowk mathcounts was def cooking with that sol!
This post has been edited 1 time. Last edited by EaZ_Shadow, Apr 6, 2025, 3:56 PM
Z
K
Y
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Y by PikaPika999
EaZ_Shadow wrote:
our team got p1 team wrong

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Y by PikaPika999, jkim0656, scannose
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Y by PikaPika999
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Y by PikaPika999
Quote:
The probability of getting consecutive coin tosses with the pattern HTT is (2/3)(1/3)(1/3)=2/27 . The expectation value of the number of tosses needed to first achieve that pattern is the reciprocal of that probability, thus 27/2.
I don't get the solution (why can you just reciprocate it?)
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Y by PikaPika999
Is MATHCOUNTS only for middle school students or also high school students or elementary students as well?
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Y by PikaPika999, huajun78, iwastedmyusername, vincentwant
huajun78 wrote:
Quote:
The probability of getting consecutive coin tosses with the pattern HTT is (2/3)(1/3)(1/3)=2/27 . The expectation value of the number of tosses needed to first achieve that pattern is the reciprocal of that probability, thus 27/2.
I don't get the solution (why can you just reciprocate it?)
Consider doing many coin tosses. Each appearance of HTT is disjoint, and the total number of HTTs is 2/27 times the number of tosses, so the expected distance to the next one is 27/2.
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i did it like dottedcaculator did, everyone was like did you p8 and they were like god that problem was actually hard, and i was like bruh its just that the probability is 2/3*1/3*1/3= 2/27 so the expected number is 27/2 lol you guys shouldve seen my friends expression when i told him that
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DottedCaculator wrote:
Consider doing many coin tosses. Each appearance of HTT is disjoint, and the total number of HTTs is 2/27 times the number of tosses, so the expected distance to the next one is 27/2.
I like how this solution fails if HTT is replaced with, say, TT. The expected number of flips is not 4 in this case.
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What you mean 2 diagrams? I think here the second situation applies. Then this becomes the easiest 8th question. The probability of HTT happen is: 2/3*1/3*1/3=2/27. Thus the expected number of trials is 27/2.
However, I think the question is kinda of wrong. Here the expected number of trials is not the expected number of flipping. The trial includes 3 flipping. At least, the question should make it more clearly what it is asking about.
However, I think the question is kinda of wrong. Here the expected number of trials is not the expected number of flipping. The trial includes 3 flipping. At least, the question should make it more clearly what it is asking about.
This post has been edited 1 time. Last edited by andrewmao1221, Apr 16, 2025, 12:29 PM
Reason: Additional thoughts
Reason: Additional thoughts
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Y by
A previous post derived the equation why
. A simple intuition is:
Let
be the number of trials for you to get one success.
. Thus:
. An even simpler intuition: If you do something with a success rate of 0.2, how many times on average will you have to do so you get one success? Oh, it is 5. How do you get it? 1/0.2

Let



Craftybutterfly wrote:
Why do you have to reciprocate the fraction?
This post has been edited 2 times. Last edited by andrewmao1221, Apr 16, 2025, 3:33 PM
Reason: typo
Reason: typo
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MC_ADe wrote:
States is a really good way to go about but realizing that after using CRT for p7 you won't have time to use states on p8 was kind of sadge
bro you don't need CRT for p7
its just like basic lcm work
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Y by
wait i just grinded units digit
and then added 40 i think, even if you use crt it is the most basic form (0, 1, 2)
and then added 40 i think, even if you use crt it is the most basic form (0, 1, 2)
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Y by RollingPanda4616, c_double_sharp
i thought the world was experiencing inflation, so why are the quality of problems in contests going down
This post has been edited 1 time. Last edited by Aaronjudgeisgoat, Apr 17, 2025, 12:38 AM
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nothing is wrong with the solution, no whining about it. Not true for HHH but good for HHT.
Andyluo wrote:
dottedcalculator, an 2x imo gold medalist has told me that the solution is wrong.
The only real solution is using states, which can be found on the AOPS mathjam
https://artofproblemsolving.com/school/mathjams-transcripts?id=716
The only real solution is using states, which can be found on the AOPS mathjam
https://artofproblemsolving.com/school/mathjams-transcripts?id=716
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Aaronjudgeisgoat wrote:
i thought the world was experiencing inflation, so why are the quality of problems in contests going down
2025 AMC 8 is significantly easier so as 2024 AMC 10
This post has been edited 1 time. Last edited by Craftybutterfly, Apr 17, 2025, 3:09 PM
Reason: :D
Reason: :D
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Aaronjudgeisgoat wrote:
i thought the world was experiencing inflation, so why are the quality of problems in contests going down
skimpflation!
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mulberrykid wrote:
nothing is wrong with the solution, no whining about it. Not true for HHH but good for HHT.
Andyluo wrote:
dottedcalculator, an 2x imo gold medalist has told me that the solution is wrong.
The only real solution is using states, which can be found on the AOPS mathjam
https://artofproblemsolving.com/school/mathjams-transcripts?id=716
The only real solution is using states, which can be found on the AOPS mathjam
https://artofproblemsolving.com/school/mathjams-transcripts?id=716
But that's the thing: if it using reciprocals works for HHT but not HHH, that means it does not work universally. It is most likely that MathCounts tried to use an incorrect shortcut that coincidentally ended up giving the same answer.
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Andyluo wrote:
dottedcalculator, an 2x imo gold medalist has told me that the solution is wrong.
The only real solution is using states, which can be found on the AOPS mathjam
https://artofproblemsolving.com/school/mathjams-transcripts?id=716
The only real solution is using states, which can be found on the AOPS mathjam
https://artofproblemsolving.com/school/mathjams-transcripts?id=716
have i been scammed
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yes.
but it is also dottedcaculator not dottedcalculator
but it is also dottedcaculator not dottedcalculator
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