Indonesian Regional MO 2022 - Part 1*
Source: Olimpiade Sains Nasional Tingkat Provinsi SMA/MA (sederajat)
August 24, 2022
IndonesiaRMO2022regionalgeometrytrapezoidperimeter
Problem Statement
The test this year was held on Monday, 22 August 2022 on 09.10-11.40 (GMT+7) for the essay section and was held on 12.05-13.30 (GMT+7) for the short answers section, which was to be done in an hour using the Moodle Learning Management System. Each problem in this section has a weight of 2 points, with 0 points for incorrect or unanswered problems, whereas in the essay section each problem has a weight of 7 points. As with last year, calculators, protractors and set squares are prohibited. (Of course abacus is also prohibited, but who uses abacus?)Anyway here are the problems.Part 1: Speed Round (60 minutes)
The problem was presented in no particular order, although here I will order it in a rough order of increasing difficulty.Problem 1. The number of positive integer solutions to the equation
is [url=https://artofproblemsolving.com/community/c6h2909996_7_digits_numbers]Problem 2. Consider the increasing sequence of all 7-digit numbers consisting of all of the following digits: . The 2024th term of the sequence is Problem 3. Suppose is a positive integer solution of the equation
The sum of all possible values of is Problem 4. It is known that is a trapezoid such that is parallel to , with the length of and . It is known that points and are on and respectively such that is parallel to . If the perimeter of trapezoid is the same as the perimeter of and , then the length of is Problem 5. Suppose is a triangle with side lengths , , and . The maximum possible area of a rectangle whose one of its sides lies on the line , and the two other vertices each lie on and is Problem 6. Suppose are natural numbers such that . The minimum possible value of is Problem 7. An equilateral triangle with a side length of is partitioned into unit equilateral triangles, and the sides of the small equilateral triangles are all parallel to the original large triangle. The number of paralellograms which are made up of the unit equilateral triangles is . Then the value of Problem 8. Define the sequence with , and for all , the following condition:
is satisfied. If , then the value of
Problem 9. Suppose is an integer polynomial such that is divisible by . If , and , then the minimum value of is Problem 10. The number of nonempty subsets of such that the sum of its elements is divisble by 4 is ; where and . The value of is