1. Adding and Subtracting Fractions

2. Objectives
Students will be able to find the least common denominator in order to add and subtract fractions with different denominators.
Students will be able to find the least common multiple in order to get the least common denominator.

3. Warm-up
How can we add
1/ /2 ?
On-line Integer Bar

4. Step 1: List prime factor of 3 and 5 3 = 5= 1 5 1 3
How to add 1/3+1/5 ?
Step 1: List prime factor of 3 and 5
3 = = 1 5 1 3 1 5 3
Least Common Denominator X X = 15

5. How to add 1/3+1/5 ?
Step 2: multiply the numerator and denominator by the same factor to make equivalent fractions. 1 3 X 5 1 5 X 3 5 15 3 15 8 15 + = + =
On-line Integer Bar

6. 12 How to add 1/6+1/12 ? Step 1: List prime factor of 3 and 5 6 = 12=
6 = = 1 2 3 1 2 2 3 1 2 2 3
Least Common Denominator 12 X X X =

7. How to add 1/6+1/12 ?
Step 2: multiply the numerator and denominator by the same factor to make equivalent fractions. 1 6 X 2 1 12 X 1 2 12 1 12 3 12 + = + =
On-line Integer Bar

8. Group Practice
GO!

9. How to add 5/8-3/6? = Step 1: List prime factor of 6 and 12 8 = 6=
8 = =
Least Common Denominator =

10. How to add 5/8 - 3/6
Step 2: multiply the numerator and denominator by the same factor to make equivalent fractions.

11. Individual practice

12. 3 4 + 5 6
(1) 5 7 - 1 4
(4) 10 20 - 3 15
(5) 6 10 - 1 3
(2) 5 12 + 3 8
(3) 5 24 + 3 12
(6)

13. More exercise Review: Find the LCM Video Clip to review LCD
Adding Fractions
Subtracting Fractions
On-line Practice
Practice (LCM)
Practice (LCD)
Adding Fractions
Subtracting Fractions