Page 399 - Basic College Mathematics with Early Integers

376 C HAPTE R 5 I RATIO, PROPORTION, AND MEASUREMENT

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4 140 = 25 n Set the cross products equal to each other.
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560 = 25 n Multiply.
560
= n Divide 560 by 25, the number multiplied by n.
25
2
n = 22 or 22.4 Simplify.
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4. INTERPRET. Check your work.This result is reasonable since it is a little over
20 cc. State your conclusion:The standard dose for a 140-lb woman is 22.4 cc.

Work Practice 2

PRACTICE 3 Example 3 Calculating Supplies Needed to Fertilize a Lawn
If a gallon of paint covers
A 50-pound bag of fertilizer covers 2400 square feet of lawn. How many bags of
400 square feet, how many
fertilizer are needed to cover a town square containing 15,360 square feet of lawn?
gallons are needed to paint a
Round the answer up to the nearest whole bag.
retaining wall that is 260 feet
long and 4 feet high? Round
the answer up to the nearest
whole gallon.

Solution:

1. UNDERSTAND. Read and reread the problem. Draw a picture.

1 bag How many
covers bags cover

… ?

Since one bag covers 2400 square feet, let’s see how many 2400’s there are in
15,360. We will estimate. The number 15,360 rounded to the nearest thousand
is 15,000 and 2400 rounded to the nearest thousand is 2000.Then
1
15,000 , 2000 = 7 or 7.5.
2
2. TRANSLATE. We’ll let n represent the unknown number. From the problem,
we know that 1 bag is to 2400 square feet as n bags is to 15,360 square feet. Copyright 2012 Pearson Education, Inc.
bags : 1 n ; bags
square feet : 2400 = 15,360 ; square feet
Answer
3. 3 gal