Adding Fractions with Unlike Denominators
1/4 + 2/3 =
3/12 + 8/12 = 11/12
4/5 - 1/3 =
12/15 - 5/15 = 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.
5 x 390 =
1,950
True or False:
4/9 + 1/6 = 10/18
False.
8/18 + 3/18 = 11/18
True or False:
4/3 - 2/7 = 1 1/21
True.
28/21 - 6/21 =
22/21 OR 1 1/21
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 least common denominator (LCD) for all of the fractions.
678/6 =
113
11/12 + 7/15 =
55/60 + 28/60 =
83/60 OR 1 23/60
11/12 - 7/15 =
55/60 - 28/60 =
27/60
reduced form: 9/20
1/6 and 4/21
LCD: 42
Add and subtract 3/4 and 1/5
15/20 and 4/20
Addition = 19/20
Subtraction= 11/20
59 x 13 =
767
1/2 + 1/3 + 1/4 =
6/12 + 4/12 + 3/12 =
13/12 OR 1 1/12
6/7 - 1/2 - 1/28 =
24/28 - 14/28 - 1/28 = 9/28
9/10, 5/6, and 2/3
LCD: 30
What are 2 ways you can get two fractions with unlike denominators to have the same denominator?
1) Find the least common denominator (LCD)
2) Multiply the two denominators by one another
Use the order of operations (PEMDAS) to make this equation true:
7 + 4 x 3 - 4 = 29
[(7 + 4) x 3] - 4 = 29
1/4 + 3/7 + 2/3 =
21/84 + 36/84 + 56/84 =
113/84 OR 1 29/84
9/10 - 1/4 - 1/3 =
54/60 - 15/60 - 20/60 = 19/60
11/14, 17/42, and 2/3
LCD: 42
What is the last step in the process of adding and subtracting fractions?
Use the order of operations (PEMDAS) to make this equation true:
10 + 1 + 3 - 7 x 2 = 14
(10 + 1 + 3 - 7) x 2 = 14