# User:MRENTHUSIASM

## Contents

- 1 User Count
- 2 Introduction
- 3 AoPS Bio
- 4 Contributions
- 4.1 1984 AIME
- 4.2 1985 AIME
- 4.3 1986 AIME
- 4.4 2009 AMC 10B
- 4.5 2009 AMC 12B
- 4.6 2020 AMC 8
- 4.7 2020 AMC 10A
- 4.8 2020 AMC 10B
- 4.9 2020 AMC 12A
- 4.10 2020 AMC 12B
- 4.11 2020 AIME I
- 4.12 2020 AIME II
- 4.13 2021 AMC 10A
- 4.14 2021 AMC 10B
- 4.15 2021 AMC 12A
- 4.16 2021 AMC 12B
- 4.17 2021 AIME I
- 4.18 2021 AIME II

## User Count

If this is your first time visiting this page, edit it by incrementing the user count below by one.

## Introduction

Hi Everyone,

I am a hedgehog who likes Message Board halping, funny pictures, emoji wars, and AoPS Wiki contributions. Keep these fun things coming!

This hedgehog represents my attitude towards math--enthusiastic and victorious!

And here is my personified self-portrait:

~MRENTHUSIASM

## AoPS Bio

Jerry graduated from Northeastern University in 2018 as a mathematics and computer science combined major. He has ten years of experience working with students. During his last two years in high school, he served as the math club president and prepared lively lectures on contest math. As a result, he inspired many kids to get interested in math and participate in math competitions (such as AMC and ARML). For the last eight years, he has worked with Math League to write math contests for students from grades 4 through 12 in the USA. Starting in 2019, he has served as an instructor and a Message Board Halper for many AoPS online classes and truly enjoyed that experience! In his mind, nothing is more rewarding than educating tomorrow’s bright minds. In his spare time, he loves contributing to the AoPS Wiki and playing chess and all sorts of board games, especially Scotland Yard and Samurai.

## Contributions

Below are my contributions to the AMC/AIME Problems' Solutions in the AoPS Wiki. I understand that in this communal Wiki, we all have to collaborate and make compromises. **In any of my solutions, if you find flaws and/or want major revisions, please contact me via my user talk page or the private messaging system before you take action. I am sure that we can work things out.**

Thank you for your cooperation, and hope you enjoy reading my solutions. :)

~MRENTHUSIASM

### 1984 AIME

- Problem 10 (Solution 3)

### 1985 AIME

- Problem 12 (Solution 7)

### 1986 AIME

- Problem 2 (Solutions 1, 2)

### 2009 AMC 10B

- Problem 1 (Solutions 1, 2, 3)

### 2009 AMC 12B

- Problem 1: same as 2009 AMC 10B Problem 1 (Solutions 1, 2, 3)

### 2020 AMC 8

### 2020 AMC 10A

- Problem 3 (Solution 3)
- Problem 5 (Solution 3)
- Problem 11 (Solution 5)
- Problem 17 (Solution 4)
- Problem 24 (Solution 11)
- Problem 25 (Solution 3)

### 2020 AMC 10B

- Problem 3 (Solution 4)
- Problem 4 (Solution 3)
- Problem 8 (Solution 4)
- Problem 13 (Solution 2)
- Problem 15 (Solution 3)
- Problem 23 (Solution 5)

### 2020 AMC 12A

- Problem 1 (Solution 3)
- Problem 6 (Solution 2)
- Problem 8: same as 2020 AMC 10A Problem 11 (Solution 2)
- Problem 9 (Remark)
- Problem 10 (Solution 5)
- Problem 15 (Remark)
- Problem 23: same as 2020 AMC 10A Problem 25 (Solution 3)
- Problem 24 (Remark)
- Problem 25 (Solution 1, Remark)

### 2020 AMC 12B

- Problem 3: same as 2020 AMC 10B Problem 3 (Solution 4)
- Problem 4: same as 2020 AMC 10B Problem 4 (Solution 3)
- Problem 5 (Solution 2)
- Problem 6 (Solution 2)
- Problem 10 (Diagram, Solution 7)
- Problem 12 (Diagram)
- Problem 13 (Solution 1)
- Problem 19: same as 2020 AMC 10B Problem 23 (Solution 5)

### 2020 AIME I

- Problem 5 (Solution 9)

### 2020 AIME II

### 2021 AMC 10A

- Problem 1 (Solution 2)
- Problem 2 (Solutions 2, 3, 4)
- Problem 3 (Solution 3)
- Problem 4 (Solutions 1, 2)
- Problem 5 (Solutions 1, 2)
- Problem 6 (Solutions 1, 2)
- Problem 7 (Solutions 2, 4)
- Problem 9 (Solution 3)
- Problem 10 (Solution 7)
- Problem 11 (Solutions 1, 3)
- Problem 12 (Solution 1)
- Problem 13 (Solution 2)
- Problem 17 (Diagram, Solution 2)
- Problem 18 (Solutions 1, 4)
- Problem 20 (Solution 2)
- Problem 22 (Solution 2)
- Problem 23 (Solution 3)
- Problem 24 (Diagram, Solution 2)
- Problem 25 (Solutions 2, 4)

### 2021 AMC 10B

- Problem 6 (Solution 3)
- Problem 7 (Solution 2)
- Problem 8 (Solution 3)
- Problem 16 (Solution 4)
- Problem 17 (Solution 3)

### 2021 AMC 12A

- Problem 2 (Solutions 2, 3)
- Problem 3: same as 2021 AMC 10A Problem 3 (Solution 3)
- Problem 4: same as 2021 AMC 10A Problem 7 (Solutions 2, 4)
- Problem 6 (Solutions 2, 3)
- Problem 7: same as 2021 AMC 10A Problem 9 (Solution 3)
- Problem 9: same as 2021 AMC 10A Problem 10 (Solution 7)
- Problem 10: same as 2021 AMC 10A Problem 12 (Solution 1)
- Problem 11 (Solutions 2, 3, 4)
- Problem 13 (Solutions 2, 3)
- Problem 14 (Solutions 2, 4)
- Problem 15 (Solutions 3, 4)
- Problem 17: same as 2021 AMC 10A Problem 17 (Diagram, Solution 2)
- Problem 18: same as 2021 AMC 10A Problem 18 (Solutions 1, 4)
- Problem 19 (Solutions 2, 3, Remark)
- Problem 21 (Solution 2, Remark)
- Problem 22 (Solution 4)
- Problem 23: same as 2021 AMC 10A Problem 23 (Solution 3)
- Problem 24 (Solution 1)
- Problem 25 (Solution 1)

### 2021 AMC 12B

- Problem 4: same as 2021 AMC 10B Problem 6 (Solution 3)
- Problem 11 (Solution 4)
- Problem 20 (Solution 4)
- Problem 21 (Solution 3)
- Problem 23 (Solution 4)

### 2021 AIME I

- Problem 1 (Solution 1)
- Problem 2 (Solution 2)
- Problem 3 (Solution 3)
- Problem 7 (Remark)
- Problem 8 (Solution 3, Remark)
- Problem 9 (Diagram, Solution 6)
- Problem 10 (Solution 2)
- Problem 11 (Solution 4)

### 2021 AIME II

- Problem 1 (Solution 3, Remark)
- Problem 2 (Solution 1)
- Problem 3 (Solution 2)
- Problem 4 (Solution 1)
- Problem 5 (Solutions 2, 5)
- Problem 6 (Solution 3)
- Problem 7 (Solution 4)
- Problem 8 (Solution 1)
- Problem 9 (Solution 2)
- Problem 10 (Diagram, Solution 3)
- Problem 11 (Solution 2)
- Problem 12 (Diagram, Solution 2)
- Problem 13 (Solution 3)
- Problem 14 (Diagram, Solution 2)
- Problem 15 (Solution 2)