1. With Unlike Denominators
Adding & Subtracting
Fractions
With Unlike Denominators

2. Adding Fractions with Like Denominators 1 2 =
Adding Fractions with UNLIKE Denominators =

3. How do you find Common Denominators?
The least common denominator, or LCD, of two fractions is the smallest number that can be divided by both denominators

4. Methods to Find the LCD
Begin listing the multiples of both denominators until you can find a common one.
4x x x x4
Multiples of 4: 4, 8, , ____________________________
Multiples of 6: 6, , 12
6x x x3 12

5. Find the Greatest Common Factor of the denominators
Finding the LCD
Find the Greatest Common Factor of the denominators
Multiply the Denominators together
Divide the product of the denominators by the Greatest Common Factor.

6. What times the denominator equals the new number? + 12 12 3 2

7. Creating the New Fractions3 4 9 12
Multiply product by the original numerator
Divide denominators + 2 12 1 6
Multiply product by the original numerator
Divide denominators
________
________

8. Add the Two Like Fractions11 12 9 12 2 12 = +

9. Check out these sites to get some more practice
Hyperlinks
Check out these sites to get some more practice
Addition-Unlike Denominators
Least Common Multiple
coolmath4kids

10. Courtesy of www.lessonplanspage.com
Try it out with a Game!
Fraction Matchin'
Everyone has a note card.
Some of you have problems with unlike denominators
Others have the corresponding common denominator
Find your match and work out the problem!
card 1 matches card 2
 1   2  +          1   4 
      4  +               4 
Courtesy of

11. Assessment Please print out your answers and submit
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