ka July Highlights and 2025 AoPS Online Class Information
jwelsh0
Jul 1, 2025
We are halfway through summer, so be sure to carve out some time to keep your skills sharp and explore challenging topics at AoPS Online and our AoPS Academies (including the Virtual Campus)!
[list][*]Over 60 summer classes are starting at the Virtual Campus on July 7th - check out the math and language arts options for middle through high school levels.
[*]At AoPS Online, we have accelerated sections where you can complete a course in half the time by meeting twice/week instead of once/week, starting on July 8th:
[list][*]MATHCOUNTS/AMC 8 Basics
[*]MATHCOUNTS/AMC 8 Advanced
[*]AMC Problem Series[/list]
[*]Plus, AoPS Online has a special seminar July 14 - 17 that is outside the standard fare: Paradoxes and Infinity
[*]We are expanding our in-person AoPS Academy locations - are you looking for a strong community of problem solvers, exemplary instruction, and math and language arts options? Look to see if we have a location near you and enroll in summer camps or academic year classes today! New locations include campuses in California, Georgia, New York, Illinois, and Oregon and more coming soon![/list]
MOP (Math Olympiad Summer Program) just ended and the IMO (International Mathematical Olympiad) is right around the corner! This year’s IMO will be held in Australia, July 10th - 20th. Congratulations to all the MOP students for reaching this incredible level and best of luck to all selected to represent their countries at this year’s IMO! Did you know that, in the last 10 years, 59 USA International Math Olympiad team members have medaled and have taken over 360 AoPS Online courses. Take advantage of our Worldwide Online Olympiad Training (WOOT) courses
and train with the best! Please note that early bird pricing ends August 19th!
Are you tired of the heat and thinking about Fall? You can plan your Fall schedule now with classes at either AoPS Online, AoPS Academy Virtual Campus, or one of our AoPS Academies around the US.
Our full course list for upcoming classes is below:
All classes start 7:30pm ET/4:30pm PT unless otherwise noted.
Prealgebra 2
Friday, Jul 25 - Nov 21
Sunday, Aug 17 - Dec 14
Tuesday, Sep 9 - Jan 13
Thursday, Sep 25 - Jan 29
Sunday, Oct 19 - Feb 22
Monday, Oct 27 - Mar 2
Wednesday, Nov 12 - Mar 18
Introduction to Algebra A
Tuesday, Jul 15 - Oct 28
Sunday, Aug 17 - Dec 14
Wednesday, Aug 27 - Dec 17
Friday, Sep 5 - Jan 16
Thursday, Sep 11 - Jan 15
Sunday, Sep 28 - Feb 1
Monday, Oct 6 - Feb 9
Tuesday, Oct 21 - Feb 24
Sunday, Nov 9 - Mar 15
Friday, Dec 5 - Apr 3
Introduction to Counting & Probability
Wednesday, Jul 2 - Sep 17
Sunday, Jul 27 - Oct 19
Monday, Aug 11 - Nov 3
Wednesday, Sep 3 - Nov 19
Sunday, Sep 21 - Dec 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Friday, Oct 3 - Jan 16
Sunday, Oct 19 - Jan 25
Tuesday, Nov 4 - Feb 10
Sunday, Dec 7 - Mar 8
Introduction to Number Theory
Tuesday, Jul 15 - Sep 30
Wednesday, Aug 13 - Oct 29
Friday, Sep 12 - Dec 12
Sunday, Oct 26 - Feb 1
Monday, Dec 1 - Mar 2
Introduction to Algebra B
Friday, Jul 18 - Nov 14
Thursday, Aug 7 - Nov 20
Monday, Aug 18 - Dec 15
Sunday, Sep 7 - Jan 11
Thursday, Sep 11 - Jan 15
Wednesday, Sep 24 - Jan 28
Sunday, Oct 26 - Mar 1
Tuesday, Nov 4 - Mar 10
Monday, Dec 1 - Mar 30
Introduction to Geometry
Monday, Jul 14 - Jan 19
Wednesday, Aug 13 - Feb 11
Tuesday, Aug 26 - Feb 24
Sunday, Sep 7 - Mar 8
Thursday, Sep 11 - Mar 12
Wednesday, Sep 24 - Mar 25
Sunday, Oct 26 - Apr 26
Monday, Nov 3 - May 4
Friday, Dec 5 - May 29
Paradoxes and Infinity
Mon, Tue, Wed, & Thurs, Jul 14 - Jul 16 (meets every day of the week!)
Sat & Sun, Sep 13 - Sep 14 (1:00 - 4:00 PM PT/4:00 - 7:00 PM ET)
Intermediate: Grades 8-12
Intermediate Algebra
Sunday, Jul 13 - Jan 18
Thursday, Jul 24 - Jan 22
Friday, Aug 8 - Feb 20
Tuesday, Aug 26 - Feb 24
Sunday, Sep 28 - Mar 29
Wednesday, Oct 8 - Mar 8
Sunday, Nov 16 - May 17
Thursday, Dec 11 - Jun 4
Precalculus
Wednesday, Aug 6 - Jan 21
Tuesday, Sep 9 - Feb 24
Sunday, Sep 21 - Mar 8
Monday, Oct 20 - Apr 6
Sunday, Dec 14 - May 31
Advanced: Grades 9-12
Calculus
Sunday, Sep 7 - Mar 15
Wednesday, Sep 24 - Apr 1
Friday, Nov 14 - May 22
Contest Preparation: Grades 6-12
MATHCOUNTS/AMC 8 Basics
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
Sunday, Aug 17 - Nov 9
Wednesday, Sep 3 - Nov 19
Tuesday, Sep 16 - Dec 9
Sunday, Sep 21 - Dec 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Monday, Oct 6 - Jan 12
Thursday, Oct 16 - Jan 22
Tues, Thurs & Sun, Dec 9 - Jan 18 (meets three times a week!)
MATHCOUNTS/AMC 8 Advanced
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
Sunday, Aug 17 - Nov 9
Tuesday, Aug 26 - Nov 11
Thursday, Sep 4 - Nov 20
Friday, Sep 12 - Dec 12
Monday, Sep 15 - Dec 8
Sunday, Oct 5 - Jan 11
Tues, Thurs & Sun, Dec 2 - Jan 11 (meets three times a week!)
Mon, Wed & Fri, Dec 8 - Jan 16 (meets three times a week!)
AMC 10 Problem Series
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)
Sunday, Aug 10 - Nov 2
Thursday, Aug 14 - Oct 30
Tuesday, Aug 19 - Nov 4
Mon & Wed, Sep 15 - Oct 22 (meets twice a week!)
Mon, Wed & Fri, Oct 6 - Nov 3 (meets three times a week!)
Tue, Thurs & Sun, Oct 7 - Nov 2 (meets three times a week!)
AMC 10 Final Fives
Friday, Aug 15 - Sep 12
Sunday, Sep 7 - Sep 28
Tuesday, Sep 9 - Sep 30
Monday, Sep 22 - Oct 13
Sunday, Sep 28 - Oct 19 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Wednesday, Oct 8 - Oct 29
Thursday, Oct 9 - Oct 30
AMC 12 Problem Series
Wednesday, Aug 6 - Oct 22
Sunday, Aug 10 - Nov 2
Monday, Aug 18 - Nov 10
Mon & Wed, Sep 15 - Oct 22 (meets twice a week!)
Tues, Thurs & Sun, Oct 7 - Nov 2 (meets three times a week!)
AMC 12 Final Fives
Thursday, Sep 4 - Sep 25
Sunday, Sep 28 - Oct 19
Tuesday, Oct 7 - Oct 28
I have seen many posts talking about commonly asked questions, such as finding the value of ,,,, why or even expressions of those terms combined as if that would make them defined. I have made this post to answer these questions once and for all, and I politely ask everyone to link this post to threads that are talking about this issue.
[list]
[*]Firstly, the case of . It is usually regarded that , not because this works numerically but because it is convenient to define it this way. You will see the convenience of defining other undefined things later on in this post.
[*]What about ? The issue here is that isn't even rigorously defined in this expression. What exactly do we mean by ? Unless the example in question is put in context in a formal manner, then we say that is meaningless.
[*]What about ? Suppose that . Then we would have , absurd. A more rigorous treatment of the idea is that does not exist in the first place, although you will see why in a calculus course. So the point is that is undefined.
[*]What about if ? An article from brilliant has a good explanation. Alternatively, you can just use a geometric series. Notice that
[*]What about ? Usually this is considered to be an indeterminate form, but I would also wager that this is also undefined.
[/list]
Hopefully all of these issues and their corollaries are finally put to rest. Cheers.
2nd EDIT (6/14/22): Since I originally posted this, it has since blown up so I will try to add additional information per the request of users in the thread below.
INDETERMINATE VS UNDEFINED
What makes something indeterminate? As you can see above, there are many things that are indeterminate. While definitions might vary slightly, it is the consensus that the following definition holds: A mathematical expression is be said to be indeterminate if it is not definitively or precisely determined. So how does this make, say, something like indeterminate? In analysis (the theory behind calculus and beyond), limits involving an algebraic combination of functions in an independent variable may often be evaluated by replacing these functions by their limits. However, if the expression obtained after this substitution does not provide sufficient information to determine the original limit, then the expression is called an indeterminate form. For example, we could say that is an indeterminate form.
But we need to more specific, this is still ambiguous. An indeterminate form is a mathematical expression involving at most two of , or , obtained by applying the algebraic limit theorem (a theorem in analysis, look this up for details) in the process of attempting to determine a limit, which fails to restrict that limit to one specific value or infinity, and thus does not determine the limit being calculated. This is why it is called indeterminate. Some examples of indeterminate forms are etc etc. So what makes something undefined? In the broader scope, something being undefined refers to an expression which is not assigned an interpretation or a value. A function is said to be undefined for points outside its domain. For example, the function given by the mapping is undefined for . On the other hand, is undefined because dividing by is not defined in arithmetic by definition. In other words, something is undefined when it is not defined in some mathematical context.
WHEN THE WATERS GET MUDDIED
So with this notion of indeterminate and undefined, things get convoluted. First of all, just because something is indeterminate does not mean it is not undefined. For example is considered both indeterminate and undefined (but in the context of a limit then it is considered in indeterminate form). Additionally, this notion of something being undefined also means that we can define it in some way. To rephrase, this means that technically, we can make something that is undefined to something that is defined as long as we define it. I'll show you what I mean.
One example of making something undefined into something defined is the extended real number line, which we define as So instead of treating infinity as an idea, we define infinity (positively and negatively, mind you) as actual numbers in the reals. The advantage of doing this is for two reasons. The first is because we can turn this thing into a totally ordered set. Specifically, we can let for each which means that via this order topology each subset has an infimum and supremum and is therefore compact. While this is nice from an analytic standpoint, extending the reals in this way can allow for interesting arithmetic! In it is perfectly OK to say that, So addition, multiplication, and division are all defined nicely. However, notice that we have some indeterminate forms here which are also undefined, So while we define certain things, we also left others undefined/indeterminate in the process! However, in the context of measure theory it is common to define as greenturtle3141 noted below. I encourage to reread what he wrote, it's great stuff! As you may notice, though, dividing by is undefined still! Is there a place where it isn't? Kind of. To do this, we can extend the complex numbers! More formally, we can define this extension as which we call the Riemann Sphere (it actually forms a sphere, pretty cool right?). As a note, means complex infinity, since we are in the complex plane now. Here's the catch: division by is allowed here! In fact, we have where and are left undefined. We also have Furthermore, we actually have some nice properties with multiplication that we didn't have before. In it holds that but and are left as undefined (unless there is an explicit need to change that somehow). One could define the projectively extended reals as we did with , by defining them as They behave in a similar way to the Riemann Sphere, with division by also being allowed with the same indeterminate forms (in addition to some other ones).
Due to excessive spam and inappropriate posts, we have locked the Prealgebra and Beginning Algebra threads.
We will either unlock these threads once we've cleaned them up or start new ones, but for now, do not start new marathon threads for these subjects. Any new marathon threads started while this announcement is up will be immediately deleted.
ki Basic Forum Rules and Info (Read before posting)
jellymoop368
NMay 16, 2018
by harry1234
f(Reminder: Do not post Alcumus or class homework questions on this forum. Instructions below.)f
Welcome to the Middle School Math Forum! Please take a moment to familiarize yourself with the rules.
Overview:
[list]
[*] When you're posting a new topic with a math problem, give the topic a detailed title that includes the subject of the problem (not just "easy problem" or "nice problem")
[*] Stay on topic and be courteous.
[*] Hide solutions!
[*] If you see an inappropriate post in this forum, simply report the post and a moderator will deal with it. Don't make your own post telling people they're not following the rules - that usually just makes the issue worse.
[*] When you post a question that you need help solving, post what you've attempted so far and not just the question. We are here to learn from each other, not to do your homework. :P
[*] Avoid making posts just to thank someone - you can use the upvote function instead
[*] Don't make a new reply just to repeat yourself or comment on the quality of others' posts; instead, post when you have a new insight or question. You can also edit your post if it's the most recent and you want to add more information.
[*] Avoid bumping old posts.
[*] Use GameBot to post alcumus questions.
[*] If you need general MATHCOUNTS/math competition advice, check out the threads below.
[*] Don't post other users' real names.
[*] Advertisements are not allowed. You can advertise your forum on your profile with a link, on your blog, and on user-created forums that permit forum advertisements.
[/list]
As always, if you have any questions, you can PM me or any of the other Middle School Moderators. Once again, if you see spam, it would help a lot if you filed a report instead of responding :)
Marathons!
Relays might be a better way to describe it, but these threads definitely go the distance! One person starts off by posting a problem, and the next person comes up with a solution and a new problem for another user to solve. Here's some of the frequently active marathons running in this forum:
[list][*]Algebra
[*]Prealgebra
[*]Proofs
[*]Factoring
[*]Geometry
[*]Counting & Probability
[*]Number Theory[/list]
Some of these haven't received attention in a while, but these are the main ones for their respective subjects. Rather than starting a new marathon, please give the existing ones a shot first.
Let ABCD be a trapeze with AD ∥ BC. M and N are the midpoints of CD and BC
respectively, and P is the common point of the lines AM and DN. If PM/AP = 4, show that
ABCD is a parallelogram.
There have been all these random but useful theorems
Please post any theorems you know, random or not, but please say whether they are random or not.
I'll start give an example: Random
British Flag Theorem:
Suppose a point P is chosen anywhere on the inside of rectangle ABCD. The formula states . Proof:
The IMAGE
Applying the Pythagorean Theorem to each of the four right triangles in the diagram, we haveSo, we haveFrom rectangles and , we have and , so the expressions above for and are equal, as desired.
Copied from AOPS practice problem
Point lies within rectangle . If ,, and , what is ? Express your answer in simplest radical form.
Source: 2014 Mathcounts Chapter Sprint #29 sol
personally i hate mixed numbers. they're rarely used in competition math and just don't make sense unless you want to estimate a value. i hate how in school they make you "simplify" everything into a mixed number or else it's wrong :(
So many people know the 24 game, where you try to create the number 24 from using other numbers, but here's a twist:
You can only use the number 24 (up to 5 times) to try to make other numbers :)
the limit is 5 times because then people could just do and so on to create any number!
honestly, I feel like with only addition, subtraction, multiplication, and division, you can't get pretty far with this, so you can use any mathematical operations!
Banned functions
, because it adds 1, and spamming it would get any number.
Hi!
I'd like to introduce the Bogus Proof Marathon.
In this marathon, simply post a bogus proof that is middle-school level and the next person will find the error. You don't have to post the real solution :P
Use classic Marathon format:
[hide=P#]a1b2c3[/hide][hide=S#]a1b2c3[/hide]
Example posts:
P(x)
:o
----- S(x)
You raised everything to a power of zero, assuming that
Hey y'all so I just started preparing for the 2026 AMC 8 and I was wondering if you could give me some suggestions on what I should do so I can get DHR. I barely practice math competition and I just started to get serious this year so my scores might be bad so here it is:
I saw many recommendations about buying AoPS books but not many about the number theory so I got the Introduction to Algebra, Introduction to Counting and Probability, and Introduction to Geometry Books. I was wondering what other suggestions that you would have for me to get better at AMC 8.
Hello! This is my second math competition I made up, this time, set in the year 2500 on a Venus base in the upper atmosphere.
This is basically AMC8 for Venusians.
2500 VIMC
What is the sum of all perfect squares less than 2500 in the form where is prime?
Equilateral triangle has Area of . If point is the midpoint of , then line is , which cuts the equilateral triangle in half. What is the sum of the perimeters of and ?
A Quadnumber is a number whose digits sum to . How many positive 3-digit quadnumbers are there? (ex. is a quadnumber because it is positive, 3-digit, and the digits sum to )
A wheel has equal sections with the numbers from to written on them. If you spin the wheel times, what is the probability that you will land on a prime number on any of the spins? (Clarification: Probability of Landing on a prime AT LEAST ONCE in the N spins)
Car A travels at a constant mph. Car B is a probabilistic car, and at the start of every hour, it gets the option for a chance of traveling at mph, an chance of traveling at mph, and a chance of traveling at mph. Once Car B decides on a speed, it acts like a normal car for the rest of the hour with a constant speed at which it picked at the start of the hour, and then the same options happen at the start of the next hour, and so on. Car A and Car B leave at the same time, and they both go in the same direction. What is the probability that Car B is right next to Car A (same speed, same position) for only hours in the next 6 hours?
If , and , and , what is the least positive value of .
If and is , what is ?
This competition is shorter than the Mars version (MIMC 2200) which was 10 questions. But this one I believe is harder than the MIMC. (designed to be, anyway) Btw here is the entire MIMC competition in case you missed it a couple weeks ago.
?
If ball A costs , and ball B costs , what is the average cost per ball if you buy of ball A and of ball B? Please write as an improper fraction
How many divisors does have?
If , then what is ?
If three distinct positive primes, , sum to 50, what is the greatest possible value of such that ?
What positive integer satisfies: ?
If a circle with radius is inscribed in a square, which is inscribed in another circle, what is the area of the outer circle minus the area of the inner circle?
What is the sum of and such that the roots of sum to and multiply to ?
If the operation , what is the largest possible value of given that is a positive integer?
How many 4-digit numbers have the property that the sum of the thousands and tens digits combined is the square of the sum of the hundreds and ones digits combined?
Pls write all solutions like this:
ex. S1 (Contest: either VIMC or MIMC)
100
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Completed problems (I'm not going to show solutions here so other people can solve it)
MIMC: 1,2,3,4,5,6,7,8,9 (9/10 done)
VIMC: 1,3,4,6,7 (5/7 done)
More generally, , it is true thatwhere the equality occurs if the system has solutions in Solution. Cauchy-Schwartz’s inequality shows Those 4 quoted inequalities can be obtained if
This post has been edited 1 time. Last edited by ytChen, Dec 14, 2024, 5:13 PM Reason: Typo
More generally, , it is true thatwhere the equality occurs if the system has solutions in Solution. Cauchy-Schwartz’s inequality shows Those 4 quoted inequalities can be obtained if
This post has been edited 3 times. Last edited by sqing, Jun 12, 2025, 4:48 PM