Page 400 - Basic College Mathematics with Early Integers

S E C T I O N 5.3 I PROPORTIONS AND PROBLEM SOLVING 377

3. SOLVE:

1 n
2400 = 15,360

1 15,360 = 2400 n Set the cross products equal to each other.
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15,360 = 2400 n Multiply.
15,360
= n Divide 15,360 by 2400, the number multiplied by n.
2400
n = 6.4 Simplify.

4. INTERPRET. Check that replacing n with 6.4 makes the proportion true. Is
1
the answer reasonable? Yes, since it’s close to 7 or 7.5. Since we must buy
2
whole bags of fertilizer, 7 bags are needed. State your conclusion: To cover
15,360 square feet of lawn, 7 bags are needed.
Work Practice 3

Concept Check You are told that 12 ounces of ground coffee will brew
enough coffee to serve 20 people. How could you estimate how much ground
coffee will be needed to serve 95 people?

Concept Check Answer
Find how much will be needed for
100 people 120 * 52 by multiplying
12 ounces by 5, which is 60 ounces.