Difference between revisions of "2022 USAJMO Problems"
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[[2022 USAJMO Problems/Problem 3|Solution]] | [[2022 USAJMO Problems/Problem 3|Solution]] | ||
+ | Let <math>b\geq2</math> and <math>w\geq2</math> be fixed integers, and <math>n=b+w</math>. Given are <math>2b</math> identical black rods and <math>2w</math> identical white rods, each of side length 1. | ||
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+ | We assemble a regular <math>2n</math>-gon using these rods so that parallel sides are the same color. Then, a convex <math>2b</math>-gon <math>B</math> is formed by translating the black rods, and a convex <math>2w</math>-gon <math>W</math> is formed by translating the white rods. An example of one way of doing the assembly when <math>b=3</math> and <math>w=2</math> is shown below, as well as the resulting polygons <math>B</math> and <math>W</math>. | ||
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+ | [image here] | ||
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+ | Prove that the difference of the areas of <math>B</math> and <math>W</math> depends only on the numbers <math>b</math> and <math>w</math>, and not on how the <math>2n</math>-gon was assembled. | ||
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==Day 2== | ==Day 2== | ||
===Problem 4=== | ===Problem 4=== |
Revision as of 20:10, 19 April 2022
Contents
[hide]Day 1
For any geometry problem whose statement begins with an asterisk , the first page of the solution must be a large, in-scale, clearly labeled diagram. Failure to meet this requirement will result in an automatic 1-point deduction.
Problem 1
For which positive integers does there exist an infinite arithmetic sequence of integers and an infinite geometric sequence of integers satisfying the following properties?
is divisible by for all integers ;
is not divisible by .
Problem 2
Let and be positive integers. The cells of an grid are colored amber and bronze such that there are at least amber cells and at least bronze cells. Prove that it is possible to choose amber cells and bronze cells such that no two of the chosen cells lie in the same row or column.
Problem 3
Solution Let and be fixed integers, and . Given are identical black rods and identical white rods, each of side length 1.
We assemble a regular -gon using these rods so that parallel sides are the same color. Then, a convex -gon is formed by translating the black rods, and a convex -gon is formed by translating the white rods. An example of one way of doing the assembly when and is shown below, as well as the resulting polygons and .
[image here]
Prove that the difference of the areas of and depends only on the numbers and , and not on how the -gon was assembled.
Day 2
Problem 4
Problem 5
Problem 6
2021 USAJMO (Problems • Resources) | ||
Preceded by 2021 USAJMO |
Followed by 2023 USAJMO | |
1 • 2 • 3 • 4 • 5 • 6 | ||
All USAJMO Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.