In Jen's baseball league, each team plays exactly 6 games against each of the other teams in the league. If a total of 396 games are played, how many teams are in the league?
(A) 12
(B) 16
(C) 15
(D) 13
(E) 9
Let the number of teams in Jen's baseball league be $n$.

Each of these $n$ teams plays 6 games against each of the $n-1$ other teams in the league.

Since there are 2 teams in each of these games, the total number of games played is $\frac{6 n(n-1)}{2}$.

The total number of games played is 396 , so $\frac{6 n(n-1)}{2}=396$ or $3 n(n-1)=396$ or $n(n-1)=132$.

The numbers $n$ and $n-1$ differ by 1 , and so we are looking for two consecutive positive integers whose product is 132 .

Since $12 \times 11=132$, the number of teams in Jen's league is 12 .