The month of May has 31 days. If the total amount of rainfall was 10 inches for the month, divide this value by the number of days in the month. In this case, you are dividing 10 by 31. This will result in a decimal value of......0.32258065. When rounding to the nearest hundredth, you will only have 2 numbers to the right of the decimal. The resulting decimal is 0.32 inches per day.