Adding and Subtracting Unlike Fractions

1
Adding and Subtracting Unlike Fractions

• Lesson 4-3

2
Rewrite the problem with equivalent fractions

• List the multiples of both denominators.
• Find the least common multiple (LCM).
• Write new fractions with the LCM as the new
  denominator.
• Find the factor you multiply by to get from your
  original denominator to your new denominator.
• Use that same factor, and multiply it by your
  original numerator to get a new numerator.

3
WHAT DOES THAT MEAN?
Lets illustrate the steps with an example.
3
1

4
6
4
3
1

4
6
9
2
x 3
x 2

12
12
11
Multiples of 4 4, 8, 12, 16, 20
12
Multiples of 6 6, 12, 18, 24, 30
5
Example 2
9
2
10, 20, 30, 40, 50
5, 10, 15, 20, 25
5
10
5
x 1
x 2
9
4

10
10
10
1

2
6
Homework Time!