infinite family of sets, each of size r, no 2 of which share < s elements
Source: 2016 Saudi Arabia IMO TST , level 4+, II p3
July 29, 2020
combinatoricssetSubsets
Problem Statement
Given two positive integers , and let be an infinite family of sets, each of size , no two of which share fewer than elements. Prove that there exists a set of size that shares at least elements with each set in .