2022 SSMO Team Round Problems

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Problem 1

In triangle $ABC$, circumcircle $\omega$ is drawn. Let $I$ be the incenter of $\triangle{ABC}$. Let $H_A$ be the intersection of the $A$-altitude and $\omega.$ Given that $AB=13,AC=15,$ and $BC=14,$ the area of triangle $AIH_A$ can be expressed as $\frac{m}{n},$ for relatively prime positive integers $m$ and $n.$ Find $m+n.$

Solution

Problem 2

Consider $8$ marbles in a line, where the color of each marble is either black or white and is randomly chosen. Define the period of a lineup of 8 marbles to be the length of the smallest lineup of marbles such that if we consider the infinite repeating sequence of marbles formed by repeating that lineup, the original lineup of 8 marbles can be found within that sequence.

A good ordering of these marbles is defined to be an ordering such that the period of the ordering is at most $6$. For example, $bwwbbbww$ is a good ordering because we may consider the lineup $bwwbb$, which has a length equal to $5.$ If the probability that the marbles form a good ordering can be expressed as $\frac{m}{n},$ where $m$ and $n$ are relatively prime positive integers, find $m+n.$

Solution

Problem 3

Let $ABCD$ be an isosceles trapezoid such that $AB\parallel CD.$ Let $E$ be a point on $CD$ such that $AB=CE.$ Let the midpoint of $DE$ be $M$ such that $BD$ intersects $AM$ at $G$ and $AE$ at $F.$ If $DC=36, AB=24,$ and $AD=10,$ then $[AGF]$ can be expressed as $\frac{m}{n},$ where $m$ and $n$ are relatively prime positive integers. Find $m+n.$

[asy] unitsize(2mm); fill((6,8/5)--(10,8/3)--(6,8)--cycle,lightgray); draw((0,0)--(36,0)--(30,8)--(6,8)--cycle); draw((6,8)--(12,0)--(0,0)); draw((0,0)--(30,8)); draw((6,8)--(6,0)); label("A", (6,8), NW); dot((6,8)); label("B", (30,8), NE); dot((30,8)); label("C", (36,0), SE); dot((36,0)); label("D", (0,0), SW); dot((0,0)); label("E",(12,0),S); dot((12,0)); label("M",(6,0),S); dot((6,0)); dot((6,8/5)); dot((10,8/3)); [/asy]

Solution

Problem 4

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Problem 5

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Problem 6

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Problem 7

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Problem 8

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Problem 9

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Problem 10

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Problem 11

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Problem 12

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Problem 13

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Problem 14

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Problem 15

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