1. Chapter 5 – 8 Add and Subtract Unlike Fractions
UNIT 2
Chapter 5 – 8 Add and Subtract Unlike Fractions

2. Adding Unlike Fractions
Rule: To add fractions with unlike denominators, rename the fractions with a common denominator. Then add and simplify.
Example: {Least Common denominator is 15}
= 1 •5 3 • •3 5 •3 {Rename each fraction using the LCD}
= {Add numerator} =

3. Adding Unlike Fractions
Example: Find = 1 • 3 4 •3 + 2 • 4 3 • 4 {LCD is 12} = = 11 12

4. Adding Mixed Number Find 1 2 9 + (-2 1 3 )
= ( ) = ( −7 3 ) {Write the mixed number as improper fractions}
= ( −7 • 3 3 • 3 ) {LCD is 9 – rename −7 3 fractions using LCD}
= ( −21 9 ) {Simplify}
= − {Add the numerators}
= {Simplify}

5. Subtracting Unlike Fractions
Rule: To subtract fractions with unlike denominators, rename the fractions with a common denominator. Then subtract and simplify.
Example: Find
= •3 7 •3 {LCD is 21- rename using LCD}
= {Subtract numerators}
= −13 21

6. Subtract Mixed Numbers
Find
= = {Write mixed numbers as improper fractions}
= 13 •5 2 • •2 5 • {Rename the fraction with the LCD of 10}
= {Subtract the numerators}
= or {Simplify}

7. Let’s Try Some Examples!
Find the sum or difference. Write in simplest form.
1) ) − ) ( )
4) ) −7 10 − 2 15

8. Let’s Check Our Answers!
Find the sum or difference. Write in simplest form.
1) ) − ) ( )
= = =
4) ) −7 10 − 2 15
= − = 5 6