Happy Thanksgiving! Please note that there are no classes November 25th-December 1st.

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k a AMC 10/12 A&B Coming up Soon!
jlacosta   0
Nov 1, 2024
There is still time to train for the November 6th and November 12th AMC 10A/12A and AMC 10B/12B, respectively! Enroll in our weekend seminars to be held on November 2nd and 3rd (listed below) and you will learn problem strategies, test taking techniques, and be able to take a full practice test! Note that the “B” seminars will have different material from the “A” seminars which were held in October.

[list][*]Special AMC 10 Problem Seminar B
[*]Special AMC 12 Problem Seminar B[/list]
For those who want to take a free practice test before the AMC 10/12 competitions, you can simulate a real competition experience by following this link. As you assess your performance on these exams, be sure to gather data!

[list][*]Which problems did you get right?
[list][*]Was the topic a strength (e.g. number theory, geometry, counting/probability, algebra)?
[*]How did you prepare?
[*]What was your confidence level?[/list]
[*]Which problems did you get wrong?
[list][list][*]Did you make an arithmetic error?
[*]Did you misread the problem?
[*]Did you have the foundational knowledge for the problem?
[*]Which topics require more fluency through practice (e.g. number theory, geometry, counting/probability, algebra)?
[*]Did you run out of time?[/list][/list]
Once you have analyzed the results with the above questions, you will have a plan of attack for future contests! BEST OF LUCK to all competitors at this year’s AMC 10 and AMC 12!

Did you know that the day after both the AMC 10A/12A and AMC 10B/12B you can join a free math jam where our AoPS team will go over the most interesting problems? Find the schedule below under “Mark your calendars”.

Mark your calendars for these upcoming free math jams!
[list][*]November 20th: Amherst College Info Session, 7:30 pm ET: Matt McGann, Dean of Admission and Financial Aid at Amherst College, and Nathan Pflueger, math professor at Amherst College, will host an info session exploring both Amherst College specifically and liberal arts colleges generally. Topics include opportunities in math, the admission process, and financial aid for both US and international students.
[*]November 7th: 2024 AMC 10/12 A Discussion, Thursday, 7:30 pm ET:
[*]AoPS instructors will discuss problems from the AMC 10/12 A, administered November 6. We will discuss some of the most interesting problems from each test!
[*]November 13th: 2024 AMC 10/12 B Discussion, Wednesday, 7:30 pm ET:
[*]AoPS instructors will discuss problems from the AMC 10/12 B, administered November 12. We will discuss some of the most interesting problems from each test![/list]
AoPS Spring classes are open for enrollment. Get a jump on the New Year and enroll in our math, contest prep, coding, and science classes today! Need help finding the right plan for your goals? Check out our recommendations page!

Don’t forget: Highlight your AoPS Education on LinkedIn!
Many of you are beginning to build your education and achievements history on LinkedIn. Now, you can showcase your courses from Art of Problem Solving (AoPS) directly on your LinkedIn profile!

Whether you've taken our classes at AoPS Online or AoPS Academies or reached the top echelons of our competition training with our Worldwide Online Olympiad Training (WOOT) program, you can now add your AoPS experience to the education section on your LinkedIn profile.

Don't miss this opportunity to stand out and connect with fellow problem-solvers in the professional world and be sure to follow us at: https://www.linkedin.com/school/art-of-problem-solving/mycompany/ Check out our job postings, too, if you are interested in either full-time, part-time, or internship opportunities!

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
Nov 1, 2024
0 replies
funny probability
Facejo   7
N 8 minutes ago by SpeedCuber7
Bob encounters an anthill while hiking and wonders whether he should destroy it. He decides to use a convoluted probabilistic scheme to decide. What is the probability that Bob will destroy the anthill if,

(a) Bob chooses a random real $r$ from $[1,\infty)$ and then destroys the anthill with probability $1/r$.

(b) Bob chooses a random integer $n$ from $[1,\infty)$ and then destroys the anthill with probability $1/n$.
7 replies
Facejo
Yesterday at 6:37 PM
SpeedCuber7
8 minutes ago
road to aime -> jmo
preCalQsus   4
N 9 minutes ago by preCalQsus
im in geometry rn, and i have amc 8 21/25 and amc 10 86.5 (That was bad).
I'm trying to at least get aime next year, and possibly USAMO/JMO in high school. I self studied the Intro to Algebra aops textbook and am currently going through Intro Number Theory and Geometry textbooks. I'm planning to just grind Alcumus for Counting and Probability and start Intermediate level classes when I have time. The problem is that I'm trying to start classes in june/july and I'm not sure how to go through the books, especially because I already have some experience with NT and Geo AMC-style problems.

Also, I'm terrible at writing proofs, but I haven't really tried to learn contest-style proofs.

Any ideas on how to get to aime next year? (my goal is to start intermediate classes and master Introductory topics)
4 replies
preCalQsus
Apr 21, 2024
preCalQsus
9 minutes ago
Number Sense Marathon (Mental Math)
brainpopper   555
N 19 minutes ago by AkCANdo
Number Sense Marathon
Hi, there isn't a number sense marathon that I know of so i'll just make one.

READ THESE RULES:
1. All calculations must be done in the head. No calculators, no paper, no writing.
2. Make problems doable. If you deem a problem too hard, skip it.
3. Please don't fight over a solution or something ridiculous.
4. Use hide tags for your problems and solutions.
5. Make all problems actually number sense. You can find a practice test for number sense here (thanks davidaops)

Don't know how to solve half the problems? Learn some tricks for mental math here.

Please make sure to follow the following format:
To post and hide your solutions, use the S# P# format. It looks like this:
[quote=User1]
S5
P6
[/quote]
[quote=User2]
S6
P7
[/quote]
To use hide tags, simply do
[code]P5[/code]to get
P5.

If you'd like to make your problems and solutions fancy, you can use LaTeX.

Lastly, please don't post if you don't know what you're doing.
555 replies
brainpopper
Jan 6, 2018
AkCANdo
19 minutes ago
How to gain speed
Dream9   4
N 3 hours ago by vsarg
I recently have trained for amc 10 and took it but now going back to amc 8, I'm so much slower. I barely meet my speed from a year ago and feel like I have no time to finish the last few problems. I think AMC 10 has helped me be able to solve all of them but severely slowed me down which sucks for amc 8. How do I get my speed up for amc 8 because I really want to do well this final year.
4 replies
Dream9
Sunday at 8:14 PM
vsarg
3 hours ago
No more topics!
Highest common factor
Mathsboy100   5
N Nov 16, 2024 by engineer48
Three number are in the ratio of \[ 3:4:5\]and
their L.C.M is 2400.Their H.C.F is
5 replies
Mathsboy100
Nov 15, 2024
engineer48
Nov 16, 2024
Highest common factor
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G H BBookmark kLocked kLocked NReply
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Mathsboy100
44 posts
#1
Y by
Three number are in the ratio of \[ 3:4:5\]and
their L.C.M is 2400.Their H.C.F is
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AbhayAttarde01
1155 posts
#2
Y by
LCM of $3,4,5$ is equal to $60$. then we divide $\frac{2400}{60}=40$, which means we multiply the ratio by $40$, so the numbers are $120,160,200$. The gcf would be $\boxed{40}$
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engineer48
811 posts
#4
Y by
AbhayAttarde01 wrote:
LCM of $3,4,5$ is equal to $60$. then we divide $\frac{2400}{60}=40$, which means we multiply the ratio by $40$, so the numbers are $120,160,200$. The gcf would be $\boxed{40}$

check 60 again
Z K Y
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Mathsboy100
44 posts
#5
Y by
Pls explain in details i do appreciate the solution
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Yiyj1
1002 posts
#7
Y by
engineer48 wrote:
AbhayAttarde01 wrote:
LCM of $3,4,5$ is equal to $60$. then we divide $\frac{2400}{60}=40$, which means we multiply the ratio by $40$, so the numbers are $120,160,200$. The gcf would be $\boxed{40}$

check 60 again

there is no problem. $\text{lcm}(3, 4, 5)=3 \cdot 4 \cdot 5 = 60$ because they are relatively prime
Mathsboy100 wrote:
Pls explain in details i do appreciate the solution

I'll try

Solution
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engineer48
811 posts
#8
Y by
oh sorry i d.c. it again
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