This website contains problems from math contests. Problems and corresponding tags were obtained from the Art of Problem Solving website.

Tags were heavily modified to better represent problems.

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Found problems: 85335

2012 Irish Math Olympiad, 3

Find, with proof, all polynomials $f$ such that $f$ has nonnegative integer coefficients, $f$($1$) = $8$ and $f$($2$) = $2012$.

2005 Tournament of Towns, 1

Can two perfect cubes fit between two consecutive perfect squares? In other words, do there exist positive integers $a$, $b$, $n$ such that $n^2 < a^3 < b^3 < (n + 1)^2$? [i](3 points)[/i]

2024 LMT Fall, 4

Tags: guts
A group of $5$ rappers wants to make a song together. They each make their own parts for the song and then arrange the $5$ parts. J Cole wants to be friends with both Drake and Kendrick, so he wants his part to be adjacent to both of theirs. Find the number of possible songs (distinct orders) that can be made.

2010 German National Olympiad, 2

Tags: inequalities
Let $a,b,c$ be pairwise distinct real numbers. Show that \[ (\frac{2a-b}{a-b})^2+(\frac{2b-c}{b-c})^2+(\frac{2c-a}{c-a})^2 \ge 5. \]

2019 Tournament Of Towns, 4

Consider the following sequence of positive real numbers $\dots<a_{-2}<a_{-1}<a_0<a_1<a_2<\dots$ infinite in both directions. For each positive integer $k$ let $b_k$ be the least integer such that the ratio between the sum of $k$ consecutive terms and the greatest of these $k$ terms is less than or equal to $b_k$(This fact occurs for any sequence of $k$ consecutive numbers). Prove that the sequence $b_1,b_2,b_3,...$ coincides with the sequence $1,2,3,...$ or is eventually constant.

2012 NIMO Summer Contest, 15

In the diagram below, square $ABCD$ with side length 23 is cut into nine rectangles by two lines parallel to $\overline{AB}$ and two lines parallel to $\overline{BC}$. The areas of four of these rectangles are indicated in the diagram. Compute the largest possible value for the area of the central rectangle. [asy] size(250); defaultpen (linewidth (0.7) + fontsize (10)); draw ((0,0)--(23,0)--(23,23)--(0,23)--cycle); label("$A$", (0,23), NW); label("$B$", (23, 23), NE); label("$C$", (23,0), SE); label("$D$", (0,0), SW); draw((0,6)--(23,6)); draw((0,19)--(23,19)); draw((5,0)--(5,23)); draw((12,0)--(12,23)); label("13", (17/2, 21)); label("111",(35/2,25/2)); label("37",(17/2,3)); label("123",(2.5,12.5));[/asy] [i]Proposed by Lewis Chen[/i]

2024 AMC 10, 24

Let \[P(m)=\frac{m}{2} + \frac{m^2}{4}+ \frac{m^4}{8} + \frac{m^8}{8}.\] How many of the values of $P(2022)$, $P(2023)$, $P(2024)$, and $P(2025)$ are integers? $ \textbf{(A) }0 \qquad \textbf{(B) }1 \qquad \textbf{(C) }2 \qquad \textbf{(D) }3 \qquad \textbf{(E) }4 \qquad $

2006 Sharygin Geometry Olympiad, 25

In the tetrahedron $ABCD$ , the dihedral angles at the $BC, CD$, and $DA$ edges are equal to $\alpha$, and for the remaining edges equal to $\beta$. Find the ratio $AB / CD$.

1996 All-Russian Olympiad Regional Round, 9.7

Prove that if $0 < a, b < 1,$ then $$\frac{ab(1 - a)(1 - b)}{(1- ab)^2 }< \frac14.$$

2023 AIME, 2

If $\sqrt{\log_bn}=\log_b\sqrt n$ and $b\log_bn=\log_bbn,$ then the value of $n$ is equal to $\frac jk,$ where $j$ and $k$ are relatively prime. What is $j+k$?

2012 Math Prize For Girls Problems, 17

How many ordered triples $(a, b, c)$, where $a$, $b$, and $c$ are from the set $\{ 1, 2, 3, \dots, 17 \}$, satisfy the equation \[ a^3 + b^3 + c^3 + 2abc = a^2b + a^2c + b^2c + ab^2 + ac^2 + bc^2 \, ? \]

2009 Stanford Mathematics Tournament, 3

Tags:
Find all integer pairs $(a, b)$ such that $ab+a-3b=5$

2024 Kosovo Team Selection Test, P1

Find all prime numbers $p$ and $q$ such that $p^q + 5q - 2$ is also a prime number.

2003 JHMMC 8, 24

Tags:
If $a + b = 13, b + c = 14, c + a = 15,$ find the value of $c$.

1977 AMC 12/AHSME, 15

[asy] size(120); real t = 2/sqrt(3); real x = 1 + sqrt(3); pair A = t*dir(90), D = x*A; pair B = t*dir(210), E = x*B; pair C = t*dir(330), F = x*C; draw(D--E--F--cycle); draw(Circle(A, 1)); draw(Circle(B, 1)); draw(Circle(C, 1)); //Credit to MSTang for the diagram[/asy] Each of the three circles in the adjoining figure is externally tangent to the other two, and each side of the triangle is tangent to two of the circles. If each circle has radius three, then the perimeter of the triangle is $\textbf{(A) }36+9\sqrt{2}\qquad\textbf{(B) }36+6\sqrt{3}\qquad\textbf{(C) }36+9\sqrt{3}\qquad\textbf{(D) }18+18\sqrt{3}\qquad \textbf{(E) }45$

2011 China Team Selection Test, 2

Let $n$ be a positive integer and let $\alpha_n $ be the number of $1$'s within binary representation of $n$. Show that for all positive integers $r$, \[2^{2n-\alpha_n}\phantom{-1} \bigg|^{\phantom{0}}_{\phantom{-1}} \sum_{k=-n}^{n} \binom{2n}{n+k} k^{2r}.\]

2023 Chile Classification NMO Seniors, 1

The function $f(x) = ax + b$ satisfies the following equalities: \begin{align*} f(f(f(1))) &= 2023, \\ f(f(f(0))) &= 1996. \end{align*} Find the value of $a$.

2013 European Mathematical Cup, 3

We are given a combination lock consisting of $6$ rotating discs. Each disc consists of digits $0, 1, 2,\ldots , 9$ in that order (after digit $9$ comes $0$). Lock is opened by exactly one combination. A move consists of turning one of the discs one digit in any direction and the lock opens instantly if the current combination is correct. Discs are initially put in the position $000000$, and we know that this combination is not correct. [list] a) What is the least number of moves necessary to ensure that we have found the correct combination? b) What is the least number of moves necessary to ensure that we have found the correct combination, if we know that none of the combinations $000000, 111111, 222222, \ldots , 999999$ is correct?[/list] [i]Proposed by Ognjen Stipetić and Grgur Valentić[/i]

2019 Saint Petersburg Mathematical Olympiad, 3

Prove that the distance between the midpoint of side $BC$ of triangle $ABC$ and the midpoint of the arc $ABC$ of its circumscribed circle is not less than $AB / 2$

2003 Moldova Team Selection Test, 4

Tags:
On the fields of a chesstable of dimensions $ n\times n$, where $ n\geq 4$ is a natural number, are being put coins. We shall consider a [i]diagonal[/i] of table each diagonal formed by at least $ 2$ fields. What is the minimum number of coins put on the table, s.t. on each column, row and diagonal there is at least one coin? Explain your answer.

1969 Putnam, A6

Tags: convergence
Let a sequence $(x_n)$ be given and let $y_n = x_{n-1} +2 x_n $ for $n>1.$ Suppose that the sequence $(y_n)$ converges. Prove that the sequence $(x_n)$ converges, too.

2017 International Olympic Revenge, 3

Tags: geometry
Let $ABC$ be a triangle, and let $P$ be a distinct point on the plane. Moreover, let $A'B'C'$ be a homothety of $ABC$ with ratio $2$ and center $P$, and let $O$ and $O'$ be the circumcenters of $ABC$ and $A'B'C'$, respectively. The circumcircles of $AB'C'$, $A'BC'$, and $A'B'C$ meet at points $X$, $Y$, and $Z$, different from $A'$, $B'$, and $C'$. In a similar way, the circumcircles of $A'BC$, $AB'C$, and $ABC'$ meet at $X'$, $Y'$, and $Z'$, different from $A$, $B$, $C$. Let $W$ and $W'$ be the circumcenters of $XYZ$ and $X'Y'Z'$, respectively. Prove that $OW$ is parallel to $O'W'$. [i]Proposed by Mateus Thimóteo, Brazil.[/i]

LMT Team Rounds 2021+, A26 B27

Tags: algebra
Chandler the Octopus along with his friends Maisy the Bear and Jeff the Frog are solving LMT problems. It takes Maisy $3$ minutes to solve a problem, Chandler $4$ minutes to solve a problem and Jeff $5$ minutes to solve a problem. They start at $12:00$ pm, and Chandler has a dentist appointment from $12:10$ pm to $12:30$, after which he comes back and continues solving LMT problems. The time it will take for them to finish solving $50$ LMT problems, in hours, is $m/n$ ,where $m$ and $n$ are relatively prime positive integers. Find $m +n$. [b]Note:[/b] they may collaborate on problems. [i]Proposed by Aditya Rao[/i]

2010 CIIM, Problem 1

Given two vectors $v = (v_1,\dots,v_n)$ and $w = (w_1\dots,w_n)$ in $\mathbb{R}^n$, lets define $v*w$ as the matrix in which the element of row $i$ and column $j$ is $v_iw_j$. Supose that $v$ and $w$ are linearly independent. Find the rank of the matrix $v*w - w*v.$

2023 Lusophon Mathematical Olympiad, 3

An integer $n$ is called $k$-special, with $k$ a positive integer, if it's the sum of the squares of $k$ consecutive integers. For example, $13$ is $2$-special, since $13=2^2+3^2$, and $2$ is $3$-special, since $2=(-1)^2+0^2+1^2$. a) Prove that there's no perfect square that is $4$-special. b) Find a perfect square that is $I^2$-special, for some odd positive integer $I$ with $I\ge 3$.