2021 AIME 1 reflection notes from H

AIME — Reflection Notes from H

Did 8 to 15 Incorrect / wrong: #9, #13, #15

Need Review / Unclear:

#9 – Not able to use similar triangles.
#13 – Totally confused; I tried PUP.
#15 – Not sure how to solve a quartic equation (x⁴).

2020 AIME I reflection notes from H

2020 AIME I - Reflection Notes from H

Did: #8–15

Had trouble / wrong: #12, #15

Need Review / Unclear:

#12 – Don’t know LTE, but I was very close to solving this using the binomial theorem.
#15 – Wasn’t able to see the symmetry: the circumcircle of IBC (with the orthocenters) is a reflection of the circumcircle of ABC.

2019 AIME I reflection notes from H

2019 AIME I — Reflection Notes from H

9 out of 15, 2 didn't finished were very close. like to know if there is better strategies for some problems.

Quick stats
• #1–5 took about 22.5 min total.
• #6 took about ~20 min (time sink).

My answers (as written)
#1: 342
#2: 029
#3: 120
#4: 122
#5: 252
#6: 090
#7: 880
#8: (very close — not finished)
#9: (wrong / crossed out)
#10: 357 (marked “silly”)
#11: ✓ (got it, but messy)
#12: (very close — basically solved but error)
#13: (basically solved, but used the wrong operation / wrong term; didn’t finish)
#14: 097
#15: (did not attempt)

Had trouble / wrong

#6 – Tried using binomial expansion, but it became too much computation (huge time sink).
#9 – Went nowhere / ended up crossing it out.
#10 – Silly mistake (need to slow down + verify).
#13 – Basically solved, but multiplied/used the wrong thing (wrong term like a_i) and didn’t finish.

Very close / almost

#8 – Very close (need to push to the finish next time).
#12 – Basically solved, but made an operation mistake (multiplied when I shouldn’t / wrong step).

Need review / improve

#11 – Got it, but I couldn’t visualize well, and the computations got messy.
#14 – Some algebra at the end felt annoying; practice finishing cleanly under time.

Not attempted

#15 – Did not attempt.

2018 AIME I reflection notes from H

2018 AIME I — Reflection Notes from H

Had trouble / wrong: #9, #10, #12, #13

Need Review / Unclear:

#9 – I got the first two terms of the final sum, but I didn’t understand / account for the double counting. a + b = 16 abd b + c = 24.

#10 – Did casework and isolated the 3’s, but wasn’t able to finish.

#12 – I got ±5 (and split into ~15 cases), but couldn’t compute after that.

#13 – Very close, but couldn’t simplify the trig at the end in the expression for the area.

2017 AIME II reflection notes from H

AIME 2017 II — Reflection Notes from H

Correct: #8, #10, #11, #12, #13

Had trouble / wrong: #9, #14, #15

Need Review / Unclear:

#9 – The “given that” statement kind of confused me. I wasn’t sure how to use it / what it was trying to tell me, so I got stuck early.

#14 – No idea how to start. I couldn’t visualize the setup, so I didn’t know what to do next.

#15 – Tried using generating functions, but it became too complicated (too many moving parts). Need a cleaner setup / approach.

2017 AIME I reflection notes from H

Correct: #8, #9, #11, #12, #14

Had trouble / wrong: #10, #13, #15

Need Review / Unclear:

#10 – Tried looking at this geometrically, but couldn’t find the right cyclic quadrilateral / setup (kept thinking about points like z₁, z₂, z₃, etc.). Need to learn how to “see” the key circle configuration faster.

#13 – I knew Q(m) would eventually become 1, but I didn’t realize it would happen at such a small value of m. This could have been done with quicker mental casework / checking small m first.

#15 – Tried using trig, but it got very complicated (too many variables). Need to practice spotting a cleaner non-trig / inequality setup sooner.

2016 AIME II reflection from H

Correct: #8, #9, #11, #12, #13, #14

Had trouble / wrong: #10, #15

Reflection / What happened:

#10 – Tried using no trig (just similar triangles + Ptolemy). Computations got messy, and I wasn’t fully confident the setup was correct.

#15 – I got pretty far into the official solution, but the step right before multiplying by Σ_i=1ⁿ(1-a_i) didn’t feel motivated to me at first (why multiply by that?). It makes more sense now, but I need to see this trick more often.

Notes:

• Cauchy–Schwarz is the right tool here and the method is clean, but it’s very tricky in execution.
• I understand the solution after reading it, but I need more problems like this to become consistent.

2016 AIME I reflection notes from H

2016 AIME I — Reflection Notes from H

Correct: #1, #2, #3, #4, #5, #7, #8, #11, #13, #14

Wrong (with notes):

#6 – My solution attempt did not include angle-chasing — that was fun/confusing for me.

#9 – Seems very tricky with a lot of variables — not sure how to even create an expression for the area using 3 variables.

#10 – Again, computation seems difficult/complex — how to simplify such problems?

#12 – Diagram seemed very complex. Additionally, the solution didn’t fully make sense. One thing I didn’t know is the radical axis theorem, which seems important.

#15 – I figured out the importance of multiple II’s and made some substitutions as such, but solutions seem to be lucky through a lot of assumptions.

2015 AIME I reflection notes from H

2015 AIME I — Reflection Notes from H

Had trouble / wrong: #9, #13, #14

Need Review / Unclear:

#9 – Got lost in casework (time sink).
#13 – Could not simplify easily; forgot identities.
#14 – Wasn’t able to visualize graph / trapezoids; need to practice these weird function graphing problems.

2011 AIME II reflection notes from H

2014 AIME I — Reflection Notes

Worked on: #8–#15

Had trouble / wrong: #8, #10, #13, #15

Need Review / Unclear:

#8 – Struggled using the Chinese Remainder Theorem.

#10 – Could not relate the turn angle to the number of rotations; needed to remember to add an extra rotation in the setup.

#13 – Was able to figure out that the center lies on EG, but was not able to use perpendicular lines correctly.

#15 – Angle chasing was difficult.

2011 AIME II reflection notes from H

2011 AIME II — Reflection Notes

Correct: 8, 9, 10, 11, 14, 15

We did #10 during our lesson already.
#15 – made a calculation error but corrected it.

Need Review / Unclear:

#12 – did not understand PIE solution (Principle of Inclusion–Exclusion).
#13 – understood the solution, but it was slightly confusing for me.

2021 spring AMC 12 B Reflection Notes from H

✅ Correct: 1–21

❌ Wrong / Unanswered:
#22 – Not sure of optimal strategy
#23 – I got stuck with cases
#24–25 – Didn’t attempt

2021 spring AMC 12 A Reflection Notes from H

2021 Spring AMC 12A — Reflection Notes

1–16 right, 15 time sink.
18, 19, 23 also right — review #19 solution.

Incorrect / Unanswered:
17, 20, 21, 22

#24, #25 → did not even look at (during the test)

At our lesson, we talked about solutions on all wrong, left blank except #25.

2016 AMC 12 A Reflection Notes from H

2016 AMC 12A Log

✅ Correct

Problems 1 → 23

❌ Wrong

Problems 24, 25

• Problem 24: Had the right idea but didn’t continue far enough.
• Problem 25: Didn’t understand the problem even after a video.

📘 Embedded Problems

Problem 24 (paraphrase)

There is a smallest positive real number a such that one can choose a positive real b making all roots of the cubic \(x^3 - a x^2 + b x - a\) real. For this minimal a, the corresponding b is unique. What is that value of b?

AoPS #24 (official)    AoPS video #24    Extra discussion

Problem 25 (paraphrase)

Let k be a positive integer. Bernardo writes perfect squares starting with the smallest having k + 1 digits; after each square, Silvia erases the last k digits of it. They continue until the final two numbers left on the board differ by at least 2. Let f(k) be the smallest positive integer that never appears on the board. Find the sum of the digits of \(f(2)+f(4)+f(6)+\cdots+f(2016)\).

Note from Mrs. Lin :  To understand this question more in details, try 

this video, starting at 24: 11. 

AoPS #25 (official)   AoPS video #25 

2017 AMC 12 B Reflection Notes from H

2017 AMC 12B — Practice Log

Quick reflections and timing notes.

Q1–Q23: all correct ✅ Q22: time sink ⏳ Q24–Q25: not answered ❌

Notable Questions

• #13: Took me a while; need to keep practicing Burnside's lemma/technique. (note to self: revisit topic & drill)
• #22: Became a time sink. Pause sooner; sketch structure, estimate difficulty, and decide quickly whether to skip.
• #24: Didn’t understand the question—unclear how to set up the average. Re-read carefully; translate wording to variables first.
• #25: Ran out of time.

Process & Timing Notes

• Not enough time at the end—was able to draw the diagram but didn’t complete the setup.
• For average/setup questions: define variables immediately, write the equation before computing.
• When a problem starts ballooning (>3–4 minutes without structure), mark and move.

Follow-Up Plan