Students and problems with constraints, find number of students
Source: 2018 Latvia BW TST P8
June 5, 2022
combinatoricscombinatorics unsolved
Problem Statement
Let natural be given. Let Laura be a student in a class of more than students, all of which participated in an olympiad and solved some problems. Additionally, it is known that:[*] for every pair of students there is exactly one problem that was solved by both students;
[*] for every pair of problems there is exactly one student who solved both of them;
[*] one specific problem was solved by Laura and exactly other students.Determine the number of students in Laura's class.