Adding Fractions with Unlike Denominators
1/4 + 2/3 =
11/12
4/5 - 1/3 =
7/15
1/2 and 3/5
LCD: 10
If the denominators are the same for two fractions, do we have to find the least common denominator (LCD)?
No, we can add or subtract the fractions as is.
4/9 + 1/6 =
*write your answer in simplest form
11/18
4/3 - 2/7 =
22/21
5/12 and 2/9
LCD: 36
What is the first thing you do when you are adding or subtracting fractions with unlike denominators?
Find the multiples of the two denominators.
3/4 + 1/9 =
31/36
3/4 - 1/9 =
23/36
1/7 and 4/8
LCD: 56
What is the THIRD step when adding and subtracting fractions with unlike denominators?
Find the Least Common Multiple/Least Common Denominator.
1/2 + 1/3 =
5/6
6/7 - 1/2 =
5/14
9/10 and 5/6
LCD: 30
What is the SECOND step in adding and subtracting fractions with unlike denominators?
Finding/identifying the common multiples.
1/4 + 3/7 =
19/28
9/10 - 1/4 =
*Write your answer in simplest form
13/20
1/4 and 2/3
LCD: 12
What is the last step in the process of adding and subtracting fractions?
Change your denominators to common denomintors and then add/subtract.