Since August and September have 61 days in total so 2nth day of October can be considered as (2n + 61)th day of August, so it is (n + 61) days after the nth day of August. Hence (n + 61) should be divisible by 7. Values of n are 2, 9, 16, 23, 30. But the last three values are discarded as 2n will be greater than 31. Hence the answer is 2.