mohs of each oly

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cowstalker

275 posts

cowstalker

#1 h Mar 23, 2025, 1:20 AM

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what are the general concencus for the mohs of each of the problems on usajmo and usamo

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blueprimes

314 posts

blueprimes

#2 h Mar 23, 2025, 1:35 AM

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JMO: (5-10) 5 (15-20) -100 5 15

This post has been edited 3 times. Last edited by blueprimes, Mar 23, 2025, 2:05 AM

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Martin2001

132 posts

Martin2001

#3 h Mar 23, 2025, 2:08 AM

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100 mohs for easy alg manip is wild

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awesomeming327.

1674 posts

awesomeming327.

#4 h Mar 23, 2025, 2:48 AM • 1 Y

Y by Jack_w

USAMO
0-10 / 20-35 / 0-30
0-5 / 20-30 / 30-50

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ScoutViolet

597 posts

ScoutViolet

#6 h Mar 23, 2025, 2:56 AM

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unbiased guy here, 5 5 15 (does it even make it) 5 10

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llddmmtt1

392 posts

llddmmtt1

#7 h Mar 23, 2025, 3:15 AM

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jmo: 0 5 15 0 0 15

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Pomansq

7 posts

Pomansq

#8 h Mar 23, 2025, 3:18 AM

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5 30 30
10 20 40

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vincentwant

1272 posts

vincentwant

#9 h Mar 23, 2025, 12:57 PM

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The time I took on p4 was 2/3 the time I took on p3. I'm not kidding.

Also I think p3 is 25 mohs. Both parts of the solution take some time and they don't share similar ideas.

This post has been edited 1 time. Last edited by vincentwant, Mar 23, 2025, 1:00 PM

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blueprimes

314 posts

blueprimes

#10 h Mar 23, 2025, 1:28 PM

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vincentwant wrote:

The time I took on p4 was 2/3 the time I took on p3. I'm not kidding.

Also I think p3 is 25 mohs. Both parts of the solution take some time and they don't share similar ideas.

I feel like the solution path for j3 is very motivated though if you just stick to the process of defining the valid sections that can be tiled then counting the paths. It's definitely not as convoluted as other 25M combo, so I think 15M makes a lot of sense.

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vincentwant

1272 posts

vincentwant

#11 h Mar 23, 2025, 1:35 PM

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blueprimes wrote:

vincentwant wrote:

The time I took on p4 was 2/3 the time I took on p3. I'm not kidding.

Also I think p3 is 25 mohs. Both parts of the solution take some time and they don't share similar ideas.

I feel like the solution path for j3 is very motivated though if you just stick to the process of defining the valid sections that can be tiled then counting the paths. It's definitely not as convoluted as other 25M combo, so I think 15M makes a lot of sense.

Both of these parts are fairly difficult and I think they're each 15-20 mohs in their own right. Also a lot of people did not solve this in contest even if they took little time on p1 and p2.

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blueprimes

314 posts

blueprimes

#12 h Mar 23, 2025, 1:45 PM

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As a comparison, USAMO 2022/1 is an example of a 25M combo. This problem is strikingly more difficult in my opinion, because first off it's very hard to start the problem, and there are several ways to approach the problem that seem plausible (global/local, induction, etc.)

J3 is a more streamlined and linear problem to solve, proving a construction for the "balanced" sections is not 15-20M in my opinion (there are very few ideas you can do here, inducting downwards seems the most natural) and feels like a <15M part. I agree with you that the computational part at the end (the $a_i + i$ substitution) is well-known but easy to get stumped on, so this is ~15M.

This post has been edited 1 time. Last edited by blueprimes, Mar 23, 2025, 1:48 PM

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vincentwant

1272 posts

vincentwant

#13 h Mar 23, 2025, 1:59 PM • 1 Y

Y by blueprimes

blueprimes wrote:

As a comparison, USAMO 2022/1 is an example of a 25M combo. This problem is strikingly more difficult in my opinion, because first off it's very hard to start the problem, and there are several ways to approach the problem that seem plausible (global/local, induction, etc.)

J3 is a more streamlined and linear problem to solve, proving a construction for the "balanced" sections is not 15-20M in my opinion (there are very few ideas you can do here, inducting downwards seems the most natural) and feels like a <15M part. I agree with you that the computational part at the end (the $a_i + i$ substitution) is well-known but easy to get stumped on, so this is ~15M.

I've solved USAMO 2022/1, and I found this problem to be comparable in difficulty
notes on 2022 U1
I also found this to be harder than USAMO 2020/2, which is 20M.

This post has been edited 1 time. Last edited by vincentwant, Mar 23, 2025, 2:07 PM

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blueprimes

314 posts

blueprimes

#14 h Mar 23, 2025, 2:08 PM • 1 Y

Y by vincentwant

While I still stand by my opinion that the methodology behind this problem is very natural, at the end of the day difficulty is subjective especially when it comes to combinatorics. If we're going based off of Evan Chen's ratings (which are arguably inflated in some cases) then yes I completely agree this problem is harder than USAMO 2020/2 (which is a 20M) which I guess directly makes this a 25M to some degree.

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Firebreather14

90 posts

Firebreather14

#15 h Mar 23, 2025, 3:08 PM

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(i did not take jmo, so take this with a grain of salt)

JMO: 5 (0-5) 20 0 5 (15-20)

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KevinChen_Yay

211 posts

KevinChen_Yay

#16 h Mar 23, 2025, 10:56 PM

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10 5 25 5 5 15 in my opinion

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aliz

157 posts

aliz

#17 h Monday at 9:19 PM

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for jmo
551501515

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arfekete

247 posts

arfekete

#18 h Yesterday at 1:01 AM

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My personal AMO rating predictions:
5/25/30, 5/15/45 (Bias: I solved 1, 4, 5 and likely partials on 2)
Range of ratings i've seen:
0-10/20-30/20-30
0-5/15-30/40-45

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