Task: Question Answering
Input (English): Passage: In May, the Tigers were as many as eight games back of the first-place 2011 Cleveland Indians season, but slowly pulled back to near-even by the All-Star break. As a three-way battle for the division title developed between the Tigers, Indians, and 2011 Chicago White Sox season, the Tigers put together an 18–10 record in August to begin to pull away. Starter Doug Fister, acquired via trade on July 30, provided an immediate spark, going 8–1 over the final two months of the season with a sparkling 1.79 ERA. After a loss on September 1, the Tigers reeled off a 12-game winning streak to put any thoughts of another late-season collapse to rest. The streak consisted of four consecutive three-game sweeps over their AL Central Division rivals. It was the Tigers longest winning streak since the 1934 Detroit Tigers season won 14 straight. On September 16, the Tigers clinched the AL Central Division title with a 3–1 win over the 2011 Oakland Athletics season. It was their first AL Central title since joining the division in 1998, and first division title of any kind since 1987 Detroit Tigers season. The Tigers clinched the division with 11 games left to play, tying the franchise record set by the 1984 Detroit Tigers season. 
Question: How many runs did the Tigers beat the Athletics by on September 16? 
Answer type: Number 
Output (English): 2.