Imagine, in the school there are 25,000 students, at least one from each of 50 states. Than must be a group of 500 students coming from same state.
I don't know what to count the 25,000 students or 500 students.
Question How can I prove the pigenhole principle in this case?
Attempt I know, If $k$ is a positive integer and $k+1$ or more objects are placed into $k$ boxes , than there is at least one box containing two or more of the objects. I don't know what to count the 25,000 students or 500 students ?