EXAMPLE 2.7.8

To determine the number (N) of 5-pound bags of ice required to reduce the temperature of water in a swimming pool by Dº Fahrenheit, use the formula N = 0.06125DV, where V is the volume of the pool (in cubic feet).

Gomer has a circular pool with a diameter of 12 feet, filled to a depth of 3 feet. How many 5-pound bags of ice are required to reduce the pool's temperature from 85º to 80º Fahrenheit?

SOLUTION

This is simply a matter of plugging appropriate values into the formula N = 0.06125DV.

Since we want to reduce the temperature of the pool's water from 85º to 80º Fahrenheit, D is equal to 5. Since pool has the shape of a cylinder whose radius is 6 feet and height is 3 feet, V, in cubic feet, is equal to pi times (6 squared) times 3. Thus, the number (N) of bags of ice is

N = 0.06125 times 5 times pi times (6 squared) times 3 = 103.9

It will require roughly 104 bags of ice.