The Formula Gives the Number, N, of Football Games

Multiple Choice

The formula gives the number, N, of football games that must be scheduled in a league with t teams if each team is to play every other team once. How many teams are in a league that schedules 55 games in such a way that each team plays every other team once?

A) 15
B) 9
C) 11
D) 10
E) 13