Stay ahead of learning milestones! Enroll in a class over the summer!

G
Topic
First Poster
Last Poster
Beams inside a cube
AOPS12142015   31
N Mar 1, 2025 by peace09
Source: USOMO 2020 Problem 2, USOJMO 2020 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:
[list=]
[*]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.
[/list]
What is the smallest positive number of beams that can be placed to satisfy these conditions?

Proposed by Alex Zhai
31 replies
AOPS12142015
Jun 21, 2020
peace09
Mar 1, 2025
Points Equidistant From a Line Segment
CountofMC   26
N Feb 26, 2025 by SomeonecoolLovesMaths
Source: 2017 AMC 10A #11, AMC 12A #8
The region consisting of all points in three-dimensional space within $3$ units of line segment $\overline{AB}$ has volume $216\pi$. What is the length $AB$?

$\textbf{(A)}\ 6\qquad\textbf{(B)}\ 12\qquad\textbf{(C)}\ 18\qquad\textbf{(D)}\ 20\qquad\textbf{(E)}\ 24$
26 replies
CountofMC
Feb 8, 2017
SomeonecoolLovesMaths
Feb 26, 2025
Cube on a Plane
djmathman   16
N Feb 4, 2025 by clarkculus
Source: 2023 AIME II/14
A cube-shaped container has vertices $A$, $B$, $C$, and $D$ where $\overline{AB}$ and $\overline{CD}$ are parallel edges of the cube, and $\overline{AC}$ and $\overline{BD}$ are diagonals of the faces of the cube. Vertex $A$ of the cube is set on a horizontal plane $\mathcal P$ so that the plane of the rectangle $ABCD$ is perpendicular to $\mathcal P$, vertex $B$ is $2$ meters above $\mathcal P$, vertex $C$ is $8$ meters above $\mathcal P$, and vertex $D$ is $10$ meters above $\mathcal P$. The cube contains water whose surface is $7$ meters above $\mathcal P$. The volume of the water is $\tfrac mn$ cubic meters, where $m$ and $n$ are relatively prime positive integers. Find $m+n$.
IMAGE
16 replies
djmathman
Feb 17, 2023
clarkculus
Feb 4, 2025
Bad Shoe Placement
happiface   15
N Feb 4, 2025 by eg4334
Source: 2014 AIME II Problem #13
Ten adults enter a room, remove their shoes, and toss their shoes into a pile. Later, a child randomly pairs each left shoe with a right shoe without regard to which shoes belong together. The probability that for every positive integer $k<5,$ no collection of $k$ pairs made by the child contains the shoes from exactly $k$ of the adults is $\tfrac{m}{n},$ where $m$ and $n$ are relatively prime positive integers. Find $m+n$.
15 replies
happiface
Mar 27, 2014
eg4334
Feb 4, 2025
Cocentric Circles of radii 3,4,5
v_Enhance   49
N Jan 23, 2025 by Mathandski
Source: 2012 AIME I Problem 13
Three concentric circles have radii $3$, $4$, and $5$. An equilateral triangle with one vertex on each circle has side length $s$. The largest possible area of the triangle can be written as $a+\frac{b}{c}\sqrt{d}$, where $a,b,c$ and $d$ are positive integers, $b$ and $c$ are relatively prime, and $d$ is not divisible by the square of any prime. Find $a+b+c+d$.
49 replies
v_Enhance
Mar 16, 2012
Mathandski
Jan 23, 2025
Stereotypical AIME Problem Types
Happyllamaalways   18
N Dec 22, 2024 by Happyllamaalways
Stereotypical AIME problem types:
1. Very bashy arithmetic
2. Simple AMC 10 level problem
3. Intimidating geometry problem that you easily kill using analytic geometry
4. Trick question
5. Logarithm algebra
6. Special-case counting
7. Normal number theory problem
8. Easy but time-consuming and bashy geometry problem
9. An either very easy or very hard counting problem
10. Borderline-impossible geometry that requires you to know a very specific formula
11. Number theory but made very diabolical
12. Advanced counting problem
13. Crazy difficult precalculus problem involving advanced trigonometry and/or complex numbers
14. Algebraic manipulation
15. “Those who know” ahh moment :skull:

Discuss your thoughts in the comments!
18 replies
Happyllamaalways
Dec 21, 2024
Happyllamaalways
Dec 22, 2024
Tfw MAA plagiarizes itself
mahaler   48
N Dec 4, 2024 by JH_K2IMO
Source: 2023 AMC 10B #17
A rectangular box $\mathcal{P}$ has distinct edge lengths $a, b,$ and $c$. The sum of the lengths of all $12$ edges of $\mathcal{P}$ is $13$, the sum of the areas of all $6$ faces of $\mathcal{P}$ is $\frac{11}{2}$, and the volume of $\mathcal{P}$ is $\frac{1}{2}$. What is the length of the longest interior diagonal connecting two vertices of $\mathcal{P}$?

$\textbf{(A)}~2\qquad\textbf{(B)}~\frac{3}{8}\qquad\textbf{(C)}~\frac{9}{8}\qquad\textbf{(D)}~\frac{9}{4}\qquad\textbf{(E)}~\frac{3}{2}$
48 replies
mahaler
Nov 15, 2023
JH_K2IMO
Dec 4, 2024
Slanted Cross-Section of Cylindrical Block of Wood
Royalreter1   30
N Dec 2, 2024 by daijobu
Source: 2015 AIME I Problem 15
A block of wood has the shape of a right circular cylinder with radius $6$ and height $8$, and its entire surface has been painted blue. Points $A$ and $B$ are chosen on the edge on one of the circular faces of the cylinder so that $\overarc{AB}$ on that face measures $120^\circ$. The block is then sliced in half along the plane that passes through point $A$, point $B$, and the center of the cylinder, revealing a flat, unpainted face on each half. The area of one of those unpainted faces is $a\cdot\pi + b\sqrt{c}$, where $a$, $b$, and $c$ are integers and $c$ is not divisible by the square of any prime. Find $a+b+c$.

IMAGE
30 replies
Royalreter1
Mar 20, 2015
daijobu
Dec 2, 2024
Nonlinear System
worthawholebean   38
N Nov 26, 2024 by pateywatey
Source: AIME 2010I Problem 9
Let $ (a,b,c)$ be the real solution of the system of equations $ x^3 - xyz = 2$, $ y^3 - xyz = 6$, $ z^3 - xyz = 20$. The greatest possible value of $ a^3 + b^3 + c^3$ can be written in the form $ \frac{m}{n}$, where $ m$ and $ n$ are relatively prime positive integers. Find $ m + n$.
38 replies
worthawholebean
Mar 17, 2010
pateywatey
Nov 26, 2024
Square Paper Folding
worthawholebean   17
N Nov 21, 2024 by eg4334
Source: AIME 2008I Problem 15
A square piece of paper has sides of length $ 100$. From each corner a wedge is cut in the following manner: at each corner, the two cuts for the wedge each start at distance $ \sqrt {17}$ from the corner, and they meet on the diagonal at an angle of $ 60^\circ$ (see the figure below). The paper is then folded up along the lines joining the vertices of adjacent cuts. When the two edges of a cut meet, they are taped together. The result is a paper tray whose sides are not at right angles to the base. The height of the tray, that is, the perpendicular distance between the plane of the base and the plane formed by the upper edges, can be written in the form $ \sqrt [n]{m}$, where $ m$ and $ n$ are positive integers, $ m < 1000$, and $ m$ is not divisible by the $ n$th power of any prime. Find $ m + n$.

IMAGE
17 replies
worthawholebean
Mar 23, 2008
eg4334
Nov 21, 2024
a