student that has at least 10 friends
Source: 2023 Greece JBMO TST P1
May 17, 2024
combinatorics
Problem Statement
A class has students. Each group consisting of three of the students meet, and choose one of the other students, A, to make him a gift. In this case, A considers each member of the group that offered him a gift as being his friend. Prove that there is a student that has at least friends.