Adding Fractions with Unlike Denominators
1/4 + 2/3 =
11/12
4/5 - 1/3 =
7/15
1/2 and 3/5
10
If the denominators are the same for two fractions, can we add or subtract them?
Yes! We can add or subtract the fractions as is.
List the factors of 18
1, 2, 3, 6, 9, 18
4/9 + 1/6 =
*Try to write your answer in simplest form
11/18
4/3 - 2/7 =
22/21
5/12 and 2/9
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.
List the factors of 30
1, 2, 3, 5, 6, 10, 15, 30
3/4 + 1/9 =
31/36
3/4 - 1/9 =
23/36
1/7 and 4/8
56
What is the THIRD step when adding and subtracting fractions with unlike denominators?
Find the Least Common Multiple/Least Common Denominator.
List the factors of 21
1, 3, 7, 21
1/2 + 1/3 =
5/6
6/7 - 1/2 =
5/14
9/10 and 5/6
30
What is the SECOND step in adding and subtracting fractions with unlike denominators?
Finding/identifying the common multiples.
List the factors of 9
1, 3, 9
1/4 + 3/7 =
19/28
9/10 - 1/4 =
13/20
1/4 and 2/3
12
What is the last step in the process of adding and subtracting fractions?
Change your denominators to common denominators and then add/subtract.
List the factors of 8
1, 2, 4, 8