MathDB
Tennis tournament

Source: Thailand MO 2023 Day 1 P4

May 11, 2023
combinatorics

Problem Statement

A table tennis tournament has 101101 contestants, where each pair of contestants will play each other exactly once. In each match, the player who gets 1111 points first is the winner, and the other the loser. At the end of the tournament, it turns out that there exist matches with scores 1111 to 00 and 1111 to 1010. Show that there exists 3 contestants A,B,CA,B,C such that the score of the losers in the matches between A,BA,B and A,CA,C are equal, but different from the score of the loser in the match between B,CB,C.