If a basketball team scores an average (arithmetic mean) of \(x\) points per game for \(n\) games and then scores \(y\)

If a basketball team scores an average (arithmetic mean) of \(x\) points per game for \(n\) games and then scores \(y\) points in its next game, what is the team's average score for the \(n+1\) games?

(A) \(\dfrac{nx+y}{n+1}\)

(B) \(x+\dfrac{y}{n+1}\)

(C) \(x+\dfrac{y}{n}\)

(D) \(\dfrac{n(x+y)}{n+1}\)

(E) \(\dfrac{x+ny}{n+1}\)

[spoiler]OA=A[/spoiler]

Source: Official Guide