Found problems: 85335
2024 HMNT, 7
Jasper and Rose are playing a game. Twenty-six $32$-ounce jugs are in a line, labeled Quart $\text{A}$ through Quart $\text{Z}$ from left to right. All twenty-six jugs are initially full. Jasper and Rose take turns making one of the following two moves:
[list]
[*] remove a positive integer number of ounces (possibly all) from the leftmost nonempty jug, or
[*] remove an [i]equal[/i] positive integer number of ounces from the two leftmost nonempty jugs, possibly
emptying them. Neither player may remove more ounces from a jug than it currently contains.
[/list]
Jasper plays first. A player’s score is the number of ounces they take from Quart $\text{Z}.$ If both players play to maximize their score, compute the maximum score that Jasper can guarantee.
2024 Korea Junior Math Olympiad, 3
Acute triangle $ABC$ satisfies $\angle A > \angle C$. Let $D, E, F$ be the points that the triangle's incircle intersects with $BC, CA, AB$, respectively, and $P$ some point on $AF$ different from $F$. The angle bisector of $\angle ABC$ meets $PQR$'s circumcircle $O$ at $L, R$. $L$ is the point closer to $B$ than $R$. $O$ meets $DF, DR$ at point $Q(\neq F, L), S(\neq R)$ respectively, and $PS$ hits segment $BC$ at $T$. Show that $T, Q, L$ are collinear.
2015 CCA Math Bonanza, I1
Michael the Mouse finds a block of cheese in the shape of a regular tetrahedron (a pyramid with equilateral triangles for all faces). He cuts some cheese off each corner with a sharp knife. How many faces does the resulting solid have?
[i]2015 CCA Math Bonanza Individual Round #1[/i]
1966 Polish MO Finals, 6
On the plane are chosen six points. Prove that the ratio of the longest distance between two points to the shortest is at least $\sqrt3$.
2019 Harvard-MIT Mathematics Tournament, 2
Let $\mathbb{N} = \{1, 2, 3, \dots\}$ be the set of all positive integers, and let $f$ be a bijection from $\mathbb{N}$ to $\mathbb{N}$. Must there exist some positive integer $n$ such that $(f(1), f(2), \dots, f(n))$ is a permutation of $(1, 2, \dots, n)$?
2012 AMC 10, 11
Externally tangent circles with centers at points $A$ and $B$ have radii of lengths $5$ and $3$, respectively. A line externally tangent to both circles intersects ray $AB$ at point $C$. What is $BC$?
$ \textbf{(A)}\ 4
\qquad\textbf{(B)}\ 4.8
\qquad\textbf{(C)}\ 10.2
\qquad\textbf{(D)}\ 12
\qquad\textbf{(E)}\ 14.4
$
2004 VTRMC, Problem 6
An enormous party has an infinite number of people. Each two people either know or don't know each other. Given a positive integer $n$, prove there are $n$ people in the party such that either they all know each other, or nobody knows each other (so the first possibility means that if $A$ and $B$ are any two of the $n$ people, then $A$ knows $B$, whereas the second possibility means that if $A$ and $B$ are any two of the $n$ people, then $A$ does not know $B$).
1995 National High School Mathematics League, 9
The number of real roots of the equation $\lg^2x-[\lg x]-2=0$ is________.
2010 Tournament Of Towns, 1
Is it possible to split all straight lines in a plane into the pairs of perpendicular lines, so that every line belongs to a single pair?
2006 Stanford Mathematics Tournament, 4
In a certain tournament bracket, a player must be defeated three times to be eliminated. If 512 contestants enter the tournament, what is the greatest number of games that could be played?
2024/2025 TOURNAMENT OF TOWNS, P7
The hostess takes a piece of meat from the fridge; kittens gather around her. Each minute, the hostess cuts a part from the piece and feeds it to one of the kittens (on her choice). Each time, the cut part is in the same proportion to the current piece. At some moment, the hostess puts the rest of the meat into the fridge. Can the hostess give the
same amount of meat in total to each kitten if
a) the number of kittens equals two; (3 marks)
b) the number of kittens equals three? (7 marks)
2020 Purple Comet Problems, 8
Patrick started walking at a constant rate along a straight road from school to the park. One hour after Patrick left, Tanya started running along the same road from school to the park. One hour after Tanya left, Jose started bicycling along the same road from school to the park. Tanya ran at a constant rate of $2$ miles per hour faster than Patrick walked, Jose bicycled at a constant rate of $7$ miles per hour faster than Tanya ran, and all three arrived at the park at the same time. The distance from the school to the park is $\frac{m}{n}$ miles, where $m$ and $n$ are relatively prime positive integers. Find $m + n$.
1995 Romania Team Selection Test, 2
Suppose that $n$ polygons of area $s = (n - 1)^2$ are placed on a polygon of area $S = \frac{n(n - 1)^2}{2}$. Prove that there exist two of the $n$ smaller polygons whose intersection has the area at least $1$.
2017 IFYM, Sozopol, 2
Prove that all positive rational numbers can be written as a fraction, which numerator and denominator are products of factorials of not necessarily different prime numbers. For example
$\frac{10}{9}=\frac{2!5!}{3!3!3!}$.
2020 HMNT (HMMO), 4
Points $G$ and $N$ are chosen on the interiors of sides $ED$ and $DO$ of unit square $DOME$, so that pentagon $GNOME$ has only two distinct side lengths. The sum of all possible areas of quadrilateral $NOME$ can be expressed as $\frac{a-b\sqrt{c}}{d}$, where $a,b,c,d$ are positive integers such that $\gcd(a,b,d) = 1$ and $c$ is square-free (i.e. no perfect square greater than $1$ divides $c$). Compute $1000a+100b+10c+d$.
2022 Greece Team Selection Test, 3
Find largest possible constant $M$ such that, for any sequence $a_n$, $n=0,1,2,...$ of real numbers, that satisfies the conditions :
i) $a_0=1$, $a_1=3$
ii) $a_0+a_1+...+a_{n-1} \ge 3 a_n - a_{n+1}$ for any integer $n\ge 1$
to be true that
$$\frac{a_{n+1}}{a_n} >M$$ for any integer $n\ge 0$.
2022 China Team Selection Test, 4
Given a positive integer $n$, find all $n$-tuples of real number $(x_1,x_2,\ldots,x_n)$ such that
\[ f(x_1,x_2,\cdots,x_n)=\sum_{k_1=0}^{2} \sum_{k_2=0}^{2} \cdots \sum_{k_n=0}^{2} \big| k_1x_1+k_2x_2+\cdots+k_nx_n-1 \big| \]
attains its minimum.
2002 Greece JBMO TST, 4
We have $100$ cards with two sides, the [i]even[/i] and the [i]odd[/i]. In each side there are written two succesive integers, in the [i]odd[/i] side and odd integer and at the back in the [i]even[/i] side the even number that follows the odd number of the [i]odd[/i] side, such that all intgers from $1$ to $200$ are used.
Student $A$ randomly choses $21$ cards and sums all the numbers of boths sides and announces as their sum the number $913$.
Student $B$ randomly choses from the remaining cards $20$ cards and sums all the numbers of boths sides and announces as their sum the number $2400$.
a) Explain why student $A$ has done an error in the addition.
b) If the correct result for student $A$ is $903$, explain why also student $B$ has done an error in the addition.
2024 AMC 8 -, 13
Buzz Bunny is hopping up and down a set of stairs, one step at a time. In how many ways can Buzz start on the ground, make a sequence of $6$ hops, and end up back on the ground? (For example, one sequence of hops is up-up-down-down-up-down.)
$\textbf{(A) }4\qquad\textbf{(B) }5\qquad\textbf{(C) }6\qquad\textbf{(D) }8\qquad\textbf{(E) }12$
2013 USAMTS Problems, 5
Niki and Kyle play a triangle game. Niki first draws $\triangle ABC$ with area $1$, and Kyle picks a point $X$ inside $\triangle ABC$. Niki then draws segments $\overline{DG}$, $\overline{EH}$, and $\overline{FI}$, all through $X$, such that $D$ and $E$ are on $\overline{BC}$, $F$ and $G$ are on $\overline{AC}$, and $H$ and $I$ are on $\overline{AB}$. The ten points must all be distinct. Finally, let $S$ be the sum of the areas of triangles $DEX$, $FGX$, and $HIX$. Kyle earns $S$ points, and Niki earns $1-S$ points. If both players play optimally to maximize the amount of points they get, who will win and by how much?
1960 Putnam, B1
Find all integer solutions $(m,n)$ to $m^{n}=n^{m}.$
2015 CentroAmerican, Problem 5
Let $ABC$ be a triangle such that $AC=2AB$. Let $D$ be the point of intersection of the angle bisector of the angle $CAB$ with $BC$. Let $F$ be the point of intersection of the line parallel to $AB$ passing through $C$ with the perpendicular line to $AD$ passing through $A$. Prove that $FD$ passes through the midpoint of $AC$.
2003 Federal Math Competition of S&M, Problem 1
Given a $\triangle ABC$ with the edges $a,b$ and $c$ and the area $S$:
(a) Prove that there exists $\triangle A_1B_1C_1$ with the sides $\sqrt a,\sqrt b$ and $\sqrt c$.
(b) If $S_1$ is the area of $\triangle A_1B_1C_1$, prove that $S_1^2\ge\frac{S\sqrt3}4$.
2003 South africa National Olympiad, 2
Given a parallelogram $ABCD$, join $A$ to the midpoints $E$ and $F$ of the opposite sides $BC$ and $CD$. $AE$ and $AF$ intersect the diagonal $BD$ in $M$ and $N$. Prove that $M$ and $N$ divide $BD$ into three equal parts.
1991 Arnold's Trivium, 45
Find the self-intersection index of the surface $x^4+y^4=1$ in the projective plane $\text{CP}^2$.