Learn how to add and subtract fractions with unlike denominators

1. M5N4 g. Add and subtract common fractions and mixed numbers with unlike denominators. How to add and subtract fractions with unlike denominatorsCreated by: Sarah Hallum

2. Step 1 Find the Least Common Multiple for the two denominators. Definitions: Denominator-bottom number in fraction Multiple-the answer to a multiplication problem between two whole numbers. Ex. 5-5, 10, 15, 20 Least Common Multiple-the first multiple two numbers have in common. Ex. 5-5, 10, 15, 20, 25 4-4, 8, 12, 16, 20, 24 LCM is 20.

3. Step 1 Find the Least Common Multiple for the two denominators. 1 2 1 3 LCM=6 2-2, 4, 6, 8, 10 3-3, 6, 9, 12, 15

4. Step 2 Make equivalent fractions that have the LCM as the denominator. Definitions: Equivalent Fraction-A fraction that is the same value as another fraction but different pieces Example: 1 2 2 4

5. Step 2 Make equivalent fractions that have the LCM as the denominator. LCM=6 1 2 1 3 1 3 2 2 2 6

6. Step 2 Make equivalent fractions that have the LCM as the denominator. LCM=6 1 2 1 3 1 3 3 3 2 6

7. Step 3 Add or subtract the new, equivalent fractions together. 3 6 2 6 5 6

8. Step 4 Simplify your answer. Definitions: Simplify-make your fraction as simple as possible 6 9 3 3 2 3

9. Step 4 Simplify your answer. 5 6 1 1 5 6 5=1, 5 6=1, 2, 3, 6

10. Answer 1 2 1 3 5 6

11. Let’s Practice 2/3 + 2/7 ½ +2/9 1/5 + ¾ 1/3 + ¼ 2/4 + ½ Check your answers on the next page.

12. Answer Key 2/3 + 2/7 = 20/21 ½ +2/9 = 13/18 1/5 + ¾ = 19/20 1/3 + ¼ = 7/12 2/4 + ½ = 4/4, 1

13. Final Note If you would like more practice, then click on the image below.