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Regional Olympiad - FBH 2014 Grade 11 Problem 4

Source: Regional Olympiad - Federation of Bosnia and Herzegovina 2014

September 24, 2018
combinatoricsacquaintance

Problem Statement

At the beginning of school year in one of the first grade classes: i)i) every student had exatly 2020 acquaintances ii)ii) every two students knowing each other had exactly 1313 mutual acquaintances iii)iii) every two students not knowing each other had exactly 1212 mutual acquaintances Find number of students in this class
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