1. 4
Rational Numbers: Positive and Negative Fractions

2. R.1 Fractions
4.4 Adding and Subtracting Signed Fractions
Objectives
Add and subtract like fractions.
Find the lowest common denominator for unlike fractions.
Add and subtract unlike fractions.
Add and subtract unlike fractions that contain variables.

3. Add and subtract like fractions.
When fractions have the same denominator, we say that they have common denominator, which makes them like fractions.

4. Add and subtract like fractions.
When fractions have different denominators, they are called unlike fractions.

5. Add and subtract like fractions.

6. Add and subtract like fractions.
Example
Find the sum

7. Add and subtract like fractions.

8. Add and subtract like fractions.
Example
Find the difference

9. Add and subtract like fractions.
Example
Find the difference

10. Find the lowest common denominator for unlike fractions.
Notice that 12 is also a common denominator for and because 2 and 3 both go into 12 evenly.

11. Find the lowest common denominator for unlike fractions.

12. Find the lowest common denominator for unlike fractions.
Example
Find the LCD for and by inspection.

13. Find the lowest common denominator for unlike fractions.
Example
Find the LCD for and by inspection.

14. Find the lowest common denominator for unlike fractions.
Example
What is the LCD for and ?

15. Find the lowest common denominator for unlike fractions.

16. Find the lowest common denominator for unlike fractions.
Example
What is the LCD for and ?

17. Add and subtract unlike fractions.

18. Add and subtract unlike fractions.
Example
Find the difference

19. Add and subtract unlike fractions.
Example
Find the sum

20. Add and subtract unlike fractions.
Example
Find the difference

21. Add and subtract unlike fractions that contain variables.
Example
Find the sum

22. Add and subtract unlike fractions that contain variables.
Example
Find the difference