MathDB

32

Part of 1977 IMO Longlists

Problems(1)

Nine men in the room - [ILL 1977]

Source:

1/11/2011
In a room there are nine men. Among every three of them there are two mutually acquainted. Prove that some four of them are mutually acquainted.
Ramsey Theorycombinatorics proposedcombinatorics