赛事资讯 - 第 61 页 - American Mathematics Competitions

2024年AMC8开考倒计时！AMC8竞赛个人如何报名？附AMC8答题常用技巧

AMC8竞赛在中国学生中具有广泛的功能和作用。它不仅可以作为学生升学的参考指标，还可以提升学生的数学思维能力和英语学习效果。参加AMC8竞赛可以展示个人实力，为进入名校打下坚实的基础。

活动形式

中英文试卷，25道选择题，40分钟，满分25分，答对一题得1分，答错不答不扣分。不允许使用计算器。

奖项设置

全球个人奖项

满分奖 Perfect Scores：获得满分25分的同学

全球卓越奖 Distinguished Honor Roll：全球排名前1%

全球优秀奖 Honor Roll：全球排名前5%

全球荣誉奖 Achievement Roll：6年级及以下在AMC8中获得15分以上

1.所在学校统一安排报名。

具体可以咨询孩子所在班级的数学老师，AMC中国组委会与多所国内优学校合作，学校可以统一报名，（AMC中国组委会或者阿思丹小程序）。

2.辅导机构代报名

国际教育课程辅导培训机构通常可以代报名，但是官方报名截止时间早，因此如果学校不能报名，家长一定早做打算。需要代报名服务的同学，可以扫码添加顾问老师领取报名表~

2024新赛季AMC8火热报名中，考位有限，抓紧预约~

AMC8答题常用技巧：

找规律：对于数列问题，可以从最简单的初始情况开始研究，尝试寻找规律。对于余数求解问题，余数往往是循环出现的，可以尝试找到规律。

特定值法：当题目要求最大值或最小值时，可以从最极端的情况开始考虑，假设变量中的一个取到其最值。在一些比例、百分比和比率问题中，如果不知道总数并且总数不影响答案，可以假设一个总数进行计算。对于不唯一确定的几何图形，可以假设特殊条件（如特殊角度或边长）进行计算。

排除法：考虑问题的可能取值范围，将范围外的选项排除。对于逻辑推理问题，可以逐个检验每个选项，排除有矛盾的选项。根据奇偶性，可以排除某些选项。

度量法：对于部分几何题，如果题目条件能够唯一确定图形，可以作出标准图。当题目条件不能唯一确定图形时，可以画出某种特殊情况下的图形，通过度量边长或角度直接得到答案。

【扫码免费领取】AMC8竞赛历年真题+重要公式汇总

AMC12竞赛成绩对申请大学有什么帮助？AMC12都有哪些奖项？

AMC12数学竞赛是一项高含金量的数学竞赛，由美国数学家协会组织。在全球名校中，AMC竞赛的认可度相当高。参加AMC12竞赛并取得良好的成绩可以提升学生申请名校的概率。

AMC12考察内容

AMC12考题重点多集中在进阶平面几何与立体几何、进阶代数、组合计数、综合数论、复数、对数与对数函数、多项式等，和AMC10竞赛相比，AMC12竞赛知识点新增：

进阶代数

复杂不等式、调和不等式、轮换不等式、柯西不等式；复杂函数问题，反函数和符合函数，三角函数和差化积、积化和差，万能公式；复数，复平面，欧拉公式，蒂莫夫公式；数学归纳法、复杂数列和极限。

进阶几何

圆相关几何进阶；数形结合，二维、三维图形的函数表达，进阶解析几何；不规则二维、三维图形的处理；二维向量、三维向量

进阶数论

二次余数，高次余数、费马圣诞节定理、费马小定理；各类丢番图方程的解法

进阶组合

随机过程和期望；复杂组合问题技巧、基本综合问题

AMC12竞赛成绩对申请大学的影响：

- AMC12竞赛成绩全球前2.5%至5%：有利于申请美国综合排名前30至50的大学。

- AMC12竞赛成绩达到全球前2.5%，或AIME成绩达到7分或以上：有利于申请美国综合排名前30的大学。

- AMC12竞赛成绩达到全球前1%，或AIME成绩达到8分或以上：有利于进入美国排名前20的大学。

在一些知名大学如麻省理工学院（MIT）、加州理工学院（Caltech）、斯坦福大学等的申请页面，会要求学生专门填写AMC竞赛成绩。

据麻省理工学院的招生官表示，如果学生提交了AMC成绩，并晋级到AIME阶段，那么进入MIT的几率约为20%。如果学生晋级到USA/JMO阶段，进入MIT的几率为50%。而如果学生晋级到IMO阶段，几乎可以确保被MIT录取。

AMC12竞赛奖项及分数线

Perfect Score

获奖条件：在竞赛中拿到满分

Honor Roll of Distinction

获奖条件：成绩达到全部参赛者的前1%

Honor Roll

获奖条件：成绩达到全部参赛者的前5%

Certificate of Achievement

获奖条件：参赛者为10年级及以下，且获得90分及以上分数

扫码咨询AMC10/12长线备考班，一站式搞定AMC10/12！

2013年USAJMO 真题及答案

Day 1

Problem 1

Are there integers $a$ and $b$ such that $a^5b+3$ and $ab^5+3$ are both perfect cubes of integers?

Problem 2

Each cell of an $m\times n$ board is filled with some nonnegative integer. Two numbers in the filling are said to be adjacent if their cells share a common side. (Note that two numbers in cells that share only a corner are not adjacent). The filling is called a garden if it satisfies the following two conditions:

(i) The difference between any two adjacent numbers is either $0$ or $1$ .

(ii) If a number is less than or equal to all of its adjacent numbers, then it is equal to $0$ .

Determine the number of distinct gardens in terms of $m$ and $n$ .

Problem 3

In triangle $ABC$ , points $P,Q,R$ lie on sides $BC,CA,AB$ respectively. Let $\omega_A$ , $\omega_B$ , $\omega_C$ denote the circumcircles of triangles $AQR$ , $BRP$ , $CPQ$ , respectively. Given the fact that segment $AP$ intersects $\omega_A$ , $\omega_B$ , $\omega_C$ again at $X,Y,Z$ respectively, prove that $YX/XZ=BP/PC$ .

Day 2

Problem 4

Let $f(n)$ be the number of ways to write $n$ as a sum of powers of $2$ , where we keep track of the order of the summation. For example, $f(4)=6$ because $4$ can be written as $4$ , $2+2$ , $2+1+1$ , $1+2+1$ , $1+1+2$ , and $1+1+1+1$ . Find the smallest $n$ greater than $2013$ for which $f(n)$ is odd.

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2014年USAJMO 真题及答案

Day 1

Problem 1

Let $a$ , $b$ , $c$ be real numbers greater than or equal to $1$ . Prove that $\min{\left (\frac{10a^2-5a+1}{b^2-5b+10},\frac{10b^2-5b+1}{c^2-5c+10},\frac{10c^2-5c+1}{a^2-5a+10}\right )}\leq abc.$ Solution

Problem 2

Let $\triangle{ABC}$ be a non-equilateral, acute triangle with $\angle A=60^\circ$ , and let $O$ and $H$ denote the circumcenter and orthocenter of $\triangle{ABC}$ , respectively.

(a) Prove that line $OH$ intersects both segments $AB$ and $AC$ .

(b) Line $OH$ intersects segments $AB$ and $AC$ at $P$ and $Q$ , respectively. Denote by $s$ and $t$ the respective areas of triangle $APQ$ and quadrilateral $BPQC$ . Determine the range of possible values for $s/t$ .

Problem 3

Let $\mathbb{Z}$ be the set of integers. Find all functions $f : \mathbb{Z} \rightarrow \mathbb{Z}$ such that $xf(2f(y)-x)+y^2f(2x-f(y))=\frac{f(x)^2}{x}+f(yf(y))$ for all $x, y \in \mathbb{Z}$ with $x \neq 0$ .

Day 2

Problem 4

Let $b\geq 2$ be an integer, and let $s_b(n)$ denote the sum of the digits of $n$ when it is written in base $b$ . Show that there are infinitely many positive integers that cannot be represented in the form $n+s_b(n)$ , where $n$ is a positive integer.

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2016年USAJMO 真题及答案

Day 1

Problem 1

The isosceles triangle $\triangle ABC$ , with $AB=AC$ , is inscribed in the circle $\omega$ . Let $P$ be a variable point on the arc $\stackrel{\frown}{BC}$ that does not contain $A$ , and let $I_B$ and $I_C$ denote the incenters of triangles $\triangle ABP$ and $\triangle ACP$ , respectively.

Prove that as $P$ varies, the circumcircle of triangle $\triangle PI_BI_C$ passes through a fixed point.

Problem 2

Prove that there exists a positive integer $n < 10^6$ such that $5^n$ has six consecutive zeros in its decimal representation.

Problem 3

Let $X_1, X_2, \ldots, X_{100}$ be a sequence of mutually distinct nonempty subsets of a set $S$ . Any two sets $X_i$ and $X_{i+1}$ are disjoint and their union is not the whole set $S$ , that is, $X_i\cap X_{i+1}=\emptyset$ and $X_i\cup X_{i+1}\neq S$ , for all $i\in\{1, \ldots, 99\}$ . Find the smallest possible number of elements in $S$ .

Day 2

Problem 4

Find, with proof, the least integer $N$ such that if any $2016$ elements are removed from the set $\{1, 2,\dots,N\}$ , one can still find $2016$ distinct numbers among the remaining elements with sum $N$ .

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2017年USAJMO 真题及答案

2017年USAJMO 真题

Day 1

Note: For any geometry problem whose statement begins with an asterisk ( $*$ ), the first page of the solution must be a large, in-scale, clearly labeled diagram. Failure to meet this requirement will result in an automatic 1-point deduction.

Problem 1

Prove that there are infinitely many distinct pairs $(a,b)$ of relatively prime positive integers $a > 1$ and $b > 1$ such that $a^b + b^a$ is divisible by $a + b.$

Problem 2

Consider the equation $\left(3x^3 + xy^2 \right) \left(x^2y + 3y^3 \right) = (x-y)^7.$

(a) Prove that there are infinitely many pairs $(x,y)$ of positive integers satisfying the equation.

(b) Describe all pairs $(x,y)$ of positive integers satisfying the equation.

Problem 3

( $*$ ) Let $ABC$ be an equilateral triangle and let $P$ be a point on its circumcircle. Let lines $PA$ and $BC$ intersect at $D$ ; let lines $PB$ and $CA$ intersect at $E$ ; and let lines $PC$ and $AB$ intersect at $F$ . Prove that the area of triangle $DEF$ is twice the area of triangle $ABC$ .

Day 2

Problem 4

Are there any triples $(a,b,c)$ of positive integers such that $(a-2)(b-2)(c-2) + 12$ is a prime that properly divides the positive number $a^2 + b^2 + c^2 + abc - 2017$ ?

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2018年USAJMO 真题及答案

2018年USAJMO 真题

Day 1

Problem 1

For each positive integer $n$ , find the number of $n$ -digit positive integers that satisfy both of the following conditions:

$\bullet$ no two consecutive digits are equal, and

$\bullet$ the last digit is a prime.

Problem 2

Let $a,b,c$ be positive real numbers such that $a+b+c=4\sqrt[3]{abc}$ . Prove that $2(ab+bc+ca)+4\min(a^2,b^2,c^2)\ge a^2+b^2+c^2.$ Solution

Problem 3

( $*$ ) Let $ABCD$ be a quadrilateral inscribed in circle $\omega$ with $\overline{AC} \perp \overline{BD}$ . Let $E$ and $F$ be the reflections of $D$ over lines $BA$ and $BC$ , respectively, and let $P$ be the intersection of lines $BD$ and $EF$ . Suppose that the circumcircle of $\triangle EPD$ meets $\omega$ at $D$ and $Q$ , and the circumcircle of $\triangle FPD$ meets $\omega$ at $D$ and $R$ . Show that $EQ = FR$ .

Day 2

Problem 4

Triangle $ABC$ is inscribed in a circle of radius 2 with $\angle ABC \geq 90^\circ$ , and $x$ is a real number satisfying the equation $x^4 + ax^3 + bx^2 + cx + 1 = 0$ , where $a=BC,b=CA,c=AB$ . Find all possible values of $x$ .

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2019年USAJMO 真题及答案

2019年USAJMO 真题

Day 1

Note: For any geometry problem whose statement begins with an asterisk $(*)$ , the first page of the solution must be a large, in-scale, clearly labeled diagram. Failure to meet this requirement will result in an automatic 1-point deduction.

Problem 1

There are $a+b$ bowls arranged in a row, numbered $1$ through $a+b$ , where $a$ and $b$ are given positive integers. Initially, each of the first $a$ bowls contains an apple, and each of the last $b$ bowls contains a pear.

A legal move consists of moving an apple from bowl $i$ to bowl $i+1$ and a pear from bowl $j$ to bowl $j-1$ , provided that the difference $i-j$ is even. We permit multiple fruits in the same bowl at the same time. The goal is to end up with the first $b$ bowls each containing a pear and the last $a$ bowls each containing an apple. Show that this is possible if and only if the product $ab$ is even.

Problem 2

Let $\mathbb Z$ be the set of all integers. Find all pairs of integers $(a,b)$ for which there exist functions $f:\mathbb Z\rightarrow\mathbb Z$ and $g:\mathbb Z\rightarrow\mathbb Z$ satisfying $f(g(x))=x+a\quad\text{and}\quad g(f(x))=x+b$ for all integers $x$ .

Problem 3

$(*)$ Let $ABCD$ be a cyclic quadrilateral satisfying $AD^2+BC^2=AB^2$ . The diagonals of $ABCD$ intersect at $E$ . Let $P$ be a point on side $\overline{AB}$ satisfying $\angle APD=\angle BPC$ . Show that line $PE$ bisects $\overline{CD}$ .

Day 2

Problem 4

$(*)$ Let $ABC$ be a triangle with $\angle ABC$ obtuse. The $A$ -excircle is a circle in the exterior of $\triangle ABC$ that is tangent to side $BC$ of the triangle and tangent to the extensions of the other two sides. Let $E, F$ be the feet of the altitudes from $B$ and $C$ to lines $AC$ and $AB$ , respectively. Can line $EF$ be tangent to the $A$ -excircle?

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2021年USAJMO 真题及答案

2021年USAJMO 真题

Day 1

$\textbf{Note:}$ For any geometry problem whose statement begins with an asterisk $(*)$ , the first page of the solution must be a large, in-scale, clearly labeled diagram. Failure to meet this requirement will result in an automatic 1-point deduction.

Problem 1

Let $\mathbb{N}$ denote the set of positive integers. Find all functions $f : \mathbb{N} \rightarrow \mathbb{N}$ such that for positive integers $a$ and $b,$ $f(a^2 + b^2) = f(a)f(b) \text{ and } f(a^2) = f(a)^2.$

Problem 2

Rectangles $BCC_1B_2,$ $CAA_1C_2,$ and $ABB_1A_2$ are erected outside an acute triangle $ABC.$ Suppose that $\angle BC_1C+\angle CA_1A+\angle AB_1B=180^{\circ}.$ Prove that lines $B_1C_2,$ $C_1A_2,$ and $A_1B_2$ are concurrent.

Problem 3

An equilateral triangle $\Delta$ of side length $L>0$ is given. Suppose that $n$ equilateral triangles with side length 1 and with non-overlapping interiors are drawn inside $\Delta$ , such that each unit equilateral triangle has sides parallel to $\Delta$ , but with opposite orientation. (An example with $n=2$ is drawn below.) $[asy] draw((0,0)--(1,0)--(1/2,sqrt(3)/2)--cycle,linewidth(0.5)); filldraw((0.45,0.55)--(0.65,0.55)--(0.55,0.55-sqrt(3)/2*0.2)--cycle,gray,linewidth(0.5)); filldraw((0.54,0.3)--(0.34,0.3)--(0.44,0.3-sqrt(3)/2*0.2)--cycle,gray,linewidth(0.5)); [/asy]$ Prove that $n \leq \frac{2}{3} L^{2}.$

Day 2

Problem 4

Carina has three pins, labeled $A, B$ , and $C$ , respectively, located at the origin of the coordinate plane. In a move, Carina may move a pin to an adjacent lattice point at distance $1$ away. What is the least number of moves that Carina can make in order for triangle $ABC$ to have area 2021?

(A lattice point is a point $(x, y)$ in the coordinate plane where $x$ and $y$ are both integers, not necessarily positive.)

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2020年USAJMO 真题及答案

2020年USAJMO 真题

Day 1

Problem 1

Let $n \geq 2$ be an integer. Carl has $n$ books arranged on a bookshelf. Each book has a height and a width. No two books have the same height, and no two books have the same width. Initially, the books are arranged in increasing order of height from left to right. In a move, Carl picks any two adjacent books where the left book is wider and shorter than the right book, and swaps their locations. Carl does this repeatedly until no further moves are possible. Prove that regardless of how Carl makes his moves, he must stop after a finite number of moves, and when he does stop, the books are sorted in increasing order of width from left to right.

Problem 2

Let $\omega$ be the incircle of a fixed equilateral triangle $ABC$ . Let $\ell$ be a variable line that is tangent to $\omega$ and meets the interior of segments $BC$ and $CA$ at points $P$ and $Q$ , respectively. A point $R$ is chosen such that $PR = PA$ and $QR = QB$ . Find all possible locations of the point $R$ , over all choices of $\ell$ .

Problem 3

An empty $2020 \times 2020 \times 2020$ cube is given, and a $2020 \times 2020$ grid of square unit cells is drawn on each of its six faces. A beam is a $1 \times 1 \times 2020$ rectangular prism. Several beams are placed inside the cube subject to the following conditions:

The two $1 \times 1$ faces of each beam coincide with unit cells lying on opposite faces of the cube. (Hence, there are $3 \cdot {2020}^2$ possible positions for a beam.)

No two beams have intersecting interiors.

The interiors of each of the four $1 \times 2020$ faces of each beam touch either a face of the cube or the interior of the face of another beam.

What is the smallest positive number of beams that can be placed to satisfy these conditions?

Day 2

Problem 4

Let $ABCD$ be a convex quadrilateral inscribed in a circle and satisfying $DA < AB = BC < CD$ . Points $E$ and $F$ are chosen on sides $CD$ and $AB$ such that $BE \perp AC$ and $EF \parallel BC$ . Prove that $FB = FD$ .

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