Write SQL query to solve given problem: What percentage of streets named 11th Street are in Alameda County?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(SUM(IIF(T1.street_name = '11th st', 1, 0)) AS REAL) * 100 / COUNT(T1.id_restaurant) FROM location AS T1 INNER JOIN geographic AS T2 ON T1.city = T2.city WHERE T2.County = 'alameda county'