Page 391 - Basic College Mathematics with Early Integers

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

PRACTICE 5 Example 5 Find the unknown number n.
Find the unknown number n.
8 5 7 = 6
n = 9 n 5
Solution:
Step 1:

7 6
n = 5

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7 5 = n 6 Set the cross products equal to each other.
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35 = n 6 Multiply.
Step 2:
35
= n Divide 35 by 6, the number multiplied by n.
6
5
5 = n
6
5
Check: Check to see that 5 is the unknown number.
6
Work Practice 5

PRACTICE 6 Example 6 Find the value of the unknown number n.
Find the value of the unknown
51 3
number n. =
15 60 -34 n
=
-2 n
Solution:
Step 1:

51 3
34 = n

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#
51 n =-34 3 Set cross products equal.
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51 n =-102 Multiply.
Step 2:
-102
n = Divide -102 by 51, the number multiplied by n.
51
n =-2 Simplify.

51 3
Check: Replace n with its value, 2.
-34 -2

51 3
34 2
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51 -2 -34 3 Copyright 2012 Pearson Education, Inc.
Answers -102 =-102 Cross products are equal,
2 so the proportion is true.
5. n = 14 6. n =-8 Work Practice 6
5