Final answer:
The bathtub with 40 gallons of water drains at 3 gallons per minute, making the total time to drain approximately 13.33 minutes or 13 minutes when rounded to the nearest minute.
Step-by-step explanation:
To determine the total time taken to drain a bathtub completely, we can make use of the rate at which the water is draining. In this case, the bathtub is filled with 40 gallons of water and drains at a rate of 3 gallons per minute. To find the total drain time, we divide the total amount of water by the rate of drainage:
Total drain time = Total gallons of water / Drain rate per minute
Total drain time = 40 gallons / 3 gallons per minute
Total drain time = 13.33 minutes, which can be rounded to the nearest minute if needed, resulting in approximately 13 minutes.