A coal mine yields 460 tons of coal every two days. How much coal is produced in five days? This problem asks for the yield produced over a given period of time, but supplies a yield for a different period of time. It is obvious that the key equation is: yield = rate X time. It is used twice. First to calculate the rate for the given yield and time. Then it is used to calculate the requested yield with the just calculated rate and the given time. Two rows are needed in the table, one for each step of the program. The result of the program is the production for 5 days.