MathDB
China TST 1986 4k circle markers

Source: China TST 1986, problem 8

May 16, 2005
combinatorics unsolvedcombinatoricspointsChordsChinaTSTTeam Selection Test

Problem Statement

Mark 4k4 \cdot k points in a circle and number them arbitrarily with numbers from 11 to 4k4 \cdot k. The chords cannot share common endpoints, also, the endpoints of these chords should be among the 4k4 \cdot k points.
i. Prove that 2k2 \cdot k pairwisely non-intersecting chords can be drawn for each of whom its endpoints differ in at most 3k13 \cdot k - 1. ii. Prove that the 3k13 \cdot k - 1 cannot be improved.