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?
Let’s 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!