1. Subtracting Like and Unlike Fractions

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 7
Multiples of 4: 4, 8, 12, 16, 20 12
Multiples of 6: 6, 12, 18, 24, 30

5. Example 2 9 2 10 10

6. Example 2 9 2 10 10 7 = 10

7. We need a common
denominator to add
these fractions. -

8. -
We need a common
denominator to add
these fractions. -
Count by 2's
2, 4, 6, 8, 10, 12, 14, 16, 18, 20
Count by 7's
7, 14, 21, 28, 35…

9. - 7 6 1 = = + 7 - 6 = 1 x 7 X 7 x 2 x 2 Make equivalent fractions.
Add the numerators = +
7 - 6 = 1
x 2 1

10. -
We need a common
denominator to
subtract a fraction
from another.
Count by 5's
5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55
Count by 11's
11, 22, 33, 44, 55, 66, 77…

11. 15 11 4 15 - 11 = 4 = = - x 5 x 5 x 11 x 11 Make equivalent fractions.
Subtract. =
= 4 -
x 11 4

12. -
We need a common
denominator to
subtract one fraction
from another.
Count by 2's
2, 4, 6, 8, 10, 12, 14, 16, 18, 20 …
Count by 10's
10, 20, 30…

13. 5 3 2 5 – 3 = 2 = - = x 5 x 5 x 1 x 1 Make equivalent fractions.
Subtract. - =
5 – 3 = 2
x 1 2