Question: Among the" Mumbai Indians" team that played in 2009, how many percent of the matches did they win?
SQL: SELECT CAST(SUM(CASE WHEN T1.Match_Winner = T2.Team_Id THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.Match_Id) FROM `Match` AS T1 INNER JOIN Team AS T2 ON T1.Team_1 = T2.Team_Id OR T1.Team_2 = T2.Team_Id WHERE T2.Team_Name = 'Mumbai Indians' AND T1.Match_Date LIKE '2009%'