Final answer:
The rate of change of the amount of water in the tank is 4 gallons per hour, which is calculated by dividing the total volume of 80 gallons by the draining time of 20 hours.
Step-by-step explanation:
The rate of change of the amount of water in the tank with respect to the number of hours it has been draining can be calculated by dividing the total change in volume by the total time the tank was draining.
Since the tank had an initial volume of 80 gallons and was drained completely over a period of 20 hours, we can use the formula:
Rate of change = Total change in volume / Total time
Substituting the known values, we get:
Rate of change = 80 gallons / 20 hours
= 4 gallons per hour.
This means that the water was draining from the tank at a constant rate of 4 gallons per hour.