MathDB
School and friends

Source: Romanian DMO 7th grade p3

March 1, 2008
pigeonhole principlecombinatorics proposedcombinatorics

Problem Statement

In a school there are 10 10 rooms. Each student from a room knows exactly one student from each one of the other 9 9 rooms. Prove that the rooms have the same number of students (we suppose that if A A knows B B then B B knows A A).
Back to ProblemsView on AoPS