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no of matches in a draw / total no of matches, 4n students tournament

Source: Thailand Mathematical Olympiad 2012 p8

August 17, 2020
combinatorics

Problem Statement

4n4n first grade students at Songkhla Primary School, including 2n2n boys and 2n2n girls, participate in a taekwondo tournament where every pair of students compete against each other exactly once. The tournament is scored as follows: \bullet In a match between two boys or between two girls, a win is worth 33 points, a draw 11 point, and a loss 00 points. \bullet In a math between a boy and a girl, if the boy wins, he receives 22 points, else he receives 00 points. If the girl wins, she receives 33 points, if she draws, she receives 22 points, and if she loses, she receives 00 points. After the tournament, the total score of each student is calculated. Let PP be the number of matches ending in a draw, and let QQ be the total number of matches. Suppose that the maximum total score is 4n14n - 1. Find P/QP/Q.