Math CentralQuandaries & Queries


Question from Alexandra, a student:

Engineers know that the amount of water lost due to evaporation is directly proportional to the surface area of the holding tanks and that the local climate causes water to evaporate at the rate of about gallon of water per hour for each square foot of water exposed to the air. About how many total gallons of waste water may enter the three tanks each day to maintain full capacity?
I know that the answer is 50x10^3 but i don't know why.


You need to know the total square footage of the surface of the three tanks. The evaporation rate is 1 gallon per hour for each square foot of surface area. There are 24 hours in a day so that's 24 gallons per square foot each day. If the correct amount is approximately 50,000 gallons in one day then the total surface area is 50,000/24 or a little more than 2,000 square feet.


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