In the same example, how long was the water volume delivered?

• A. 6 hours
• B. 12 hours
• C. 24 hours
• D. 48 hours

Answer: (C)

To figure how long the water volume was delivered, use the relation time equals volume divided by delivery rate. The example provides a total volume and the rate at which water was delivered, so you solve t = V / Q. The data in the example are such that dividing the volume by the rate yields 24 hours, which is why the correct duration is 24 hours.

For intuition, delivering the same volume takes more time at a slower rate and less time at a faster rate. For instance, if the volume were 480,000 gallons and the delivery rate were 20,000 gallons per hour, you’d get 480,000 / 20,000 = 24 hours. The other options would only be correct if the given V and Q produced those values, which they don’t in this scenario.