MathDB
MTRP SUBJECTIVE Q1

Source: MTRP 2024

March 16, 2024
combinatorics

Problem Statement

The Integration Premier League has nn teams competing. The tournament follows a round-robin system, that is, where every pair of teams play each other exactly once. So every team plays exactly n1n-1 matches. The top mnm \leq n temas at the end of the tournament qualify for the playoffs. Assume there are no tied matches.
Let A(m,n)A(m,n) be the minimum number of matches a team has to win to gurantee selection for the playoffs, regardless of what their run rate is. For example, A(n,n)=0A(n,n) = 0 (everyone qualifies anyway so no need to win!) and A(1,n)=n1A(1,n) = n-1 (even if you lose to just one other team, they might defeat everyone and qualify instead of you). Answer the following: (A)(A) FInd the value of A(2,4),A(2,6)A(2,4),A(2,6) and A(4,10)A(4,10) with proof (explain why a smaller value can still lead to the team not qualifying, and show that the respective values themselves are enough). (B)(B) Show that A(n1,n)=n2A(n-1,n) = \frac{n}{2} when nn even and =n+12 = \frac{n+1}{2} when nn odd. (C)(C) For bonus marks, try to find a general pattern for A(m,n)A(m,n).