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% use [nosolutions] flag to hide solutions.
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% use [solutions] flag to show solutions.
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\documentclass[
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solutions
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]{../../../lib/tex/ormc_handout}
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\usepackage{../../../lib/tex/macros}
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\usepackage{subfiles}
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\usepackage{graphicx}
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\graphicspath{ {./images} }
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\uptitlel{Intermediate 2}
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\uptitler{\smallurl{}}
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\title{Warm - Up}
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\subtitle{
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Prepared by Mark on \today \\
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\medskip
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These problems were originally found in \\
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Boris Kordemsky's \textit{The Moscow Puzzles}
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}
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\begin{document}
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\maketitle
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\subfile{problems/217}
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\vfill
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\pagebreak
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\subfile{problems/101}
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\vfill
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\pagebreak
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{The Courageous Garrison}
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A courageous garrison was defending a snow fort. The commander arranged his forces as shown in the square frame (the inner square showing the garrison's total strength of 40 boys): 11 boys defending each side of the fort.
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\begin{figure}[h]
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\centering
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\includegraphics[width=12cm]{101a}
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\end{figure}
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The garrison ``lost'' 4 boys during each of the first, second, third, and fourth assaults and 2 during the fifth and last. But after each charge 11 boys defended each side of the snow fort. How?
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\vfill
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\begin{figure}[h]
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\centering
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\includegraphics[width=4cm]{101b}
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\end{figure}
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{Knight's Move}
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To solve this problem you need not be a chess player. You need only know the way a knight moves on the chessboard: two squares in one direction and one square at right angles to the first direction. The diagram shows 16 black pawns on a board.
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\begin{figure}[h]
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\centering
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\includegraphics[width=12cm]{110}
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\end{figure}
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Can a knight capture all 16 pawns in 16 moves?
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{One Hundred and Forty-Five Doors}
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A prisoner was thrown into a medieval dungeon with 145 doors. Nine, shown by black bars, are locked, but each one will open if before you reach it you pass through exactly 8 open doors. \\
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You don't have to go through every open door but you do have to go through every cell and all 9 locked doors. If you enter a cell or go through a door a second time, the doors clang shut, trapping you. \\
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\medskip
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The prisoner (in the lower right corner cell) had a drawing of the dungeon. He thought a long time before he set out. He went through all the locked doors and escaped through the last, upper left corner one. What was his route?
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\begin{figure}[h]
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\centering
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\includegraphics[width=8cm]{120}
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\end{figure}
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\begin{figure}[h]
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\centering
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\includegraphics[width=8cm]{120}
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\end{figure}
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{How Does the Prisoner Escape?}
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This dungeon has $49$ cells. In $7$ cells ($A$ to $G$ in the diagram) there is a locked door (black bar). The keys are in cells $a$ to $g$ respectively. The other doors open only from one side, as shown. \\
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\medskip
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How does the prisoner in cell $O$ escape? He can pass through any door any number of times and need not unlock the doors in any special order. His aim is to get the key from cell $g$ and use it to escape through cell $G$
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\vfill
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\begin{figure}[h]
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\centering
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\includegraphics[width=8cm]{121}
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\end{figure}
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\vfill
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Extra copies of the dungeon are on the next page.
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\pagebreak
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\vfill
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\begin{figure}[h]
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\centering
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\includegraphics[width=8cm]{121}
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\end{figure}
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\vfill
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\begin{figure}[h]
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\centering
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\includegraphics[width=8cm]{121}
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\end{figure}
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\vfill
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\pagebreak
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{Mutual Aid}
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During the rebuilding after World War II, the Soviet Union was short of tractors. The machine and tractor stations would lend each other equipment as needed. Three machine and tractor stations were neighbors. The first lent the second and third as many tractors as they each already had. A few months later, the second lent the first and third as many as they each had. Still later, the third lent the first and second as many as they each already had. Each station now had 24 tractors. How many tractors did each station originally have?
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{The Air Parade}
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Volodya asked, ``What plane did you fly during the air parade?'' His father sketched a formation of 9 planes.
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\begin{figure}[h]
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\centering
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\includegraphics[width=9cm]{239}
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\end{figure}
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``The number of planes to the right of me multiplied by the number of planes to the left of me is 3 less than it would have been if my plane had been 3 places to the right of me.'' How did Volodya solve the problem?
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{An Elephant and a Mosquito}
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Does the weight of an elephant equal the weight of a mosquito? Let $x$ be the weight of an elephant, and $y$ that of a mosquito.
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\begin{figure}[h]
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\centering
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\includegraphics[width=10cm]{252}
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\end{figure}
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Call the sum of the two weights $2v$, then $x + y = 2v$.
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From this equation we can obtain two more:
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\[
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x - 2v = -y \text{; } x = - y + 2v
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\]
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Multiply:
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\[
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x^2 - 2vx = y^2 - 2vy
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\]
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Add $v^2$:
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\[
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x^2 - 2vx + v^2 = y^2 - 2vy + v^2 \text{, or } (x - v)^2 = (y - v)^2
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\]
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Take square roots:
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\[
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x - v = y - v \text{; } x = y
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\]
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That is, the elephant's weight ($x$) equals the mosquito's weight ($y$). What is wrong here?
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{The Lucas Problem}
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This problem was invented by Edouard Lucas, a French nineteenth-century mathematician. \\
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``Every day at noon,'' Lucas said, ``a ship leaves Le Havre for New York and another ship leaves New York for Le Havre. The trip lasts 7 days and 7 nights. How many New York-Le Havre ships will the ship leaving Le Havre today meet during its journey to New York? Can you answer graphically?
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\begin{figure}[h]
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\centering
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\includegraphics[width=10cm]{255}
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\end{figure}
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\end{document}
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\documentclass[../main.tex]{subfiles}
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\begin{document}
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\problem{A Shooting Match}
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Andryusha, Borya, and Volodya each fired 6 shots, and each got 71 points.
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\begin{figure}[h]
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\centering
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\includegraphics[width=8cm]{263}
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\end{figure}
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Andryusha's first 2 shots got 22 points and Volodya's first shot got only 3 points. \\
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Who hit the bull's-eye?
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\end{document}
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# Game ideas
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- Math dominos:
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- Each problem is a domino tile, by difficulty.
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- Score is sum if 1st try, max if 2nd try. Subtract min if no solution.
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- Each team can have 2-3 dominos at a time. No free swaps.
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- Pick up dominos without knowing problem.
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- что-где-когда:
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- All teams solve one problem at once.
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- Spacewar!:
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- Two teams, each starts in one root node.
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- Graph of problems, symmetric across middle
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- easy problems close, hard problems far.
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- Goal: capture as many nodes as possible
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- Solve a problem, capture a node
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- solve a problem on the other team's side, capture their node.
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- TODO: a fun way to resolve conflicts?
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# Topics:
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- Divisibility proofs & properties
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- 1 exists ==> assume 2 exist
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- <= , >= ==> =
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- pidgeonhole
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# Handout ideas:
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- Notation toolbox
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- Propositional logic
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- Rubik's group
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- Graph combinatorics
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- Fourier transforms
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- Probabilistic proofs
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- Bayesian / Frequentist probability
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- Data structures
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# Handouts to clean up:
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- Euler's number
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- Lattices
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- Nim handout
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- Stocks
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# Problems to record:
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- Nikita: weight of 100 cows
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- Seat swapping: everyone wants a seat that's not their own, no two people want the same seat. Each cycle, everyone swaps. Min # of cycles? Solution: 2, reflect. use even and odd cycles. Takeaway: composition of reflections is rotation.
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- Geometric optimization: ant on cube shortest path, ant on brick shortest path, ribbon on brick (over-under, h-shape) minimal length, Farthest point from corner of brick
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- 180: Sperner lemma and brouwer theorem
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- 25 horses. 5 at a time. find top 3? (7 races)
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- Telescoping sums
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- Division algorithm
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- Peano axions
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- Proof basics
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- Show that irrational
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- Voting systems
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- Weighings
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# Beginners 1
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Grades 2 - 4
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- Basic cyphers
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- Modular Arithmetic
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- Numbers in other bases
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# Beginners 2:
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Grades 4 - 6
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- Pidgeonhole principle
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- Combinatorics
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- N choose K (c and p)
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- stars and bars
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- Induction
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- Boosted induction (cauchy, etc)
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- Compass-and-Ruler constructions
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# Intermediate 1:
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Grades 5 - 7
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- Graphs
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- Instant Insanity
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- Euler walks and paths
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- Konigsberg
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- Logs & Slide rules
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- Vectors and Applications
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- Probability
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- Monty Hall problem
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# Intermediate 2:
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Grades 6 - 9
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# Advanced 1:
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Grades 9 - 10
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- Linear Algebra Basics
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- Graph Theory
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- Algorithms:
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- Ford-Fulkerson
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- Dijkstra
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- Minimal spanning tree
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- Three-color theorem
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# Advanced 2:
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Grades 11 - 12
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- Logic
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- Exists, forall, not. (Definable sets handout)
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- Mockingbird, lambda
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- Numerical cryptography
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- Group Theory
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- Understand Euler's Number
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- Relations
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