10) Amit and Sumit can plough a field in 4 days; sumit alone can plough the field in 6 days. In how many days will amit alone plough the field?

Step 1: First, we need to find out how much of the field Amit and Sumit can plough together in one day. Since they can plough the entire field in 4 days, they can plough 1/4 of the field in one day.

Step 2: Next, we need to find out how much of the field Sumit can plough alone in one day. Since Sumit can plough the entire field in 6 days, he can plough 1/6 of the field in one day.

Step 3: To find out how much of the field Amit can plough alone in one day, we subtract the amount Sumit can plough from the amount they can plough together. So, Amit can plough 1/4 - 1/6 = 1/12 of the field in one day.

Step 4: Finally, to find out how many days Amit will take to plough the entire field alone, we take the reciprocal of the fraction of the field he can plough in one day. So, Amit will take 12 days to plough the entire field alone.