Page 389 - Basic College Mathematics with Early Integers

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

2 4
PRACTICE 2 Example 2 Is = a true proportion?
3 6
3 4
Is = a true proportion? Solution:
6 8
Cross products
# #
2 6 3 4
2 = 4
3 6

#
2 6 # Are cross products equal?
3 4
12 = 12 Equal, so proportion is true.
Since the cross products are equal, the proportion is true.
Work Practice 2

4.1 2.9
PRACTICE 3 Example 3 Is = a true proportion?
7 5
3.6 5.4
Is = a true proportion? Solution:
6 8
Cross products
# #
4.1 5 7 2.9
4.1 = 2.9
7 5

#
7 2.9
4.1 5 # Are cross products equal?
20.5 Z 20.3 Not equal, so proportion is false.
4.1 2.9
Since the cross products are not equal, Z . The proportion is false.
7 5
Work Practice 3

1 1
1
PRACTICE 4 Example 4 Is 6 = 2 a true proportion?
1 1
1 3 10 4
4 3 2 2
5 10
Is = a true Solution:
1 5
2 1
3 6 1Z q
proportion?
10q 4q

1 1 1 1
1 # 4 10 # Are cross products equal?
6 2 2 2
7 9 21 1
# # Write mixed numbers as improper fractions.
6 2 2 2
21 21
= Equal, so proportion is true.
4 4
Since the cross products are equal, the proportion is true. Copyright 2012 Pearson Education, Inc.

Work Practice 4
Answers
2. yes 3. no 4. yes