Question

calculate the average annual precipitation

Answer 1

The formula for finding an  average is easy to apply. The average  equals the sum of all the items  (in this case, rainfall measurements for  a day, week, or month) divided  by the number of items (however many  days, weeks, or months you’ve  added up).[7] If you're looking for average weekly rainfall over 4 weeks, with   recorded weekly rainfall totals of 20 inches, 12 inches, 6 inches, and   25 inches, we would say 20 + 12 + 6 + 25 = 63 (the sum of the items) /   by 4 (the number of weeks) = 15.75 inches average weekly rainfall.