MathDB
Bosnia and Herzegovina JBMO TST 2010 Problem 4

Source: Bosnia and Herzegovina Junior Balkan Mathematical Olympiad TST 2010

September 17, 2018
Circle inversionclockwisecombinatorics

Problem Statement

On circle in clockwise order are written positive integers from 11 to 20102010. Let us cross out number 11, then number 1010, then number 1919, and so on every 99th number in that direction. Which number will be first crossed out twice? How many numbers at that moment are not crossed out?
Back to ProblemsView on AoPS