Write SQL query to solve given problem: How many games were sold on the DS platform on average in the 4 different regions?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT SUM(T1.num_sales) * 100000 / 4 FROM region_sales AS T1 INNER JOIN game_platform AS T2 ON T1.game_platform_id = T2.id INNER JOIN platform AS T3 ON T2.platform_id = T3.id WHERE T3.platform_name = 'DS'