Question 437841: An average family of four uses roughly 1200 liters (about 300 gallons) of water per day. (One liter = 1000 cm3) How much depth would a lake lose per year if it uniformly covered an area of 50 square kilometers and supplied a local town with a population of 40,000 people? Consider only population uses, and neglect evaporation and so on.
Answer by htmentor(1343)   (Show Source):
You can put this solution on YOUR website! A family of 4 uses 1200 liters of water per day
1200 liters/day * 365 days/year = 438000 liters per year
If the town has 40,000 people, this equals 10,000 families
So the total town usage in one year = 10000*438000 = 4.38E9 liters = 4.38E12 cm^3 (scientific notation)
The area of the lake in cm^2 is 50 km^2 * (100 cm / m)^2 * (1000 m / km)^2 = 5E11 cm^2
The loss of volume of the lake is 5E11 cm^2 * h, where h is the change in depth
The total volume of water used by the town = the volume lost by the lake.
Therefore 4.38E12/5E11 = h = 8.76 cm
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