Each of $$300$$ students belongs to exactly $$2$$ of the $$5$$ school clubs. What is the average number of students in each club? 
Overseas Competition->Knowledge Point->Counting Modules->Statistics and Probability
Since $$300$$ students belong to $$2$$ clubs each, there are $$600$$ club memberships. The average membership of the $$5$$ clubs is $$600\div 5 = 120$$ students. 