11 theatrical groups at a festival watch each other
Source: Canadian Mathematical Olympiad - 1981 - Problem 5.
May 27, 2011
floor functioncombinatorics unsolvedcombinatorics
Problem Statement
theatrical groups participated in a festival. Each day, some of the groups were scheduled to perform while the remaining groups joined the general audience. At the conclusion of the festival, each group had seen, during its days off, at least performance of every other group. At least how many days did the festival last?