Page 247 - Basic College Mathematics with Early Integers

224 C HAPTE R 3 I FRACTIONS

Concept Check Find and correct the error in the following:
2 4 6 3
+ = =
9 11 20 10
2 3
PRACTICE 4 Example 4 Subtract: -
5 20
7 5
Subtract: - Solution:
12 24
Step 1: The LCD of the denominators 5 and 20 is 20.
8
2 2 4 = 3 3
Step 2: = # = ; The fraction already has a denominator of 20.
5 5 4 20 20 20
2 3 8 3 5
Step 3: - = - =
5 20 20 20 20
Step 4: Write in simplest form.
1
5 5 1
= =
#
20 5 4 4
1
Work Practice 4
2 10
PRACTICE 5 Example 5 Subtract: -
3 11
5 9
Subtract: - Solution:
7 10
Step 1: The LCD of the denominators 3 and 11 is 33.
22
2 2 11 = 10 10 3 30
Step 2: = # = # =
3 3 11 33 11 11 3 33
2 10 22 30 –8 8
Step 3: - = - = or-
3 11 33 33 33 33
8
Step 4: - is in simplest form.
33
Work Practice 5
3 1 6
PRACTICE 6 Example 6 Find: - - +
4 14 7
5 1 1
Find: - - Solution:
8 3 12 The LCD of the denominators 4, 14, and 7 is 28.

#
#
#
3 1 6 3 7 1 2 6 4
– - + =– - +
#
#
#
4 14 7 4 7 14 2 7 4
Answers 21 2 24
=- - +
3 13 5 28 28 28
4. 5. - 6.
8 70 24 1
=
28
Concept Check Answers
Work Practice 6
When adding or subtracting fractions, we
don’t add or subtract the denominators.
Correct solutions: Copyright 2012 Pearson Education, Inc.
Concept Check Find and correct the error in the following:
2 4 22 36 58
+ = + =
9 11 99 99 99
7 3 4 1
7 3 7 9 2 1 - = =
- = - =- =- 12 4 8 2
12 4 12 12 12 6