This math topic focuses on the skill of finding the lowest common denominator (LCD) to aid in the addition of fractions with different denominators. There are seven problems provided which present pairs of fractions, and the challenge is to identify the correct LCD that would be used to add each pair. Multiple choice answers are given for each problem, testing the ability to accurately calculate or determine the least common multiple of denominators, central in simplifying addition of fractions. This topic is part of a broader unit on mixed fraction addition and subtraction.

Work on practice problems directly here, or download the printable pdf worksheet to practice offline.

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Fraction Addition - Find Common Denominator - Mixed - Two Changed Denominators Worksheet

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Fraction Addition - Find Common Denominator - Mixed - Two Changed Denominators
1
What lowest common denominator would you use to add these fractions?
A LaTex expression showing 36 over 7 + 1 over 2
a
14
b
19
c
7
d
21
e
22
f
17
2
What lowest common denominator would you use to add these fractions?
A LaTex expression showing 18 over 11 + 1 over 5
a
55
b
20
c
90
d
70
e
15
f
50
3
What lowest common denominator would you use to add these fractions?
A LaTex expression showing 21 over 3 + 15 over 7
a
33
b
37
c
17
d
21
e
15
f
9
4
What lowest common denominator would you use to add these fractions?
A LaTex expression showing 21 over 2 + 11 over 5
a
6
b
13
c
10
d
14
e
9
f
18
5
What lowest common denominator would you use to add these fractions?
A LaTex expression showing 17 over 11 + 1 over 2
a
40
b
24
c
10
d
38
e
14
f
22
6
What lowest common denominator would you use to add these fractions?
A LaTex expression showing 13 over 7 + 1 over 2
a
22
b
20
c
23
d
14
e
9
f
12
7
What lowest common denominator would you use to add these fractions?
A LaTex expression showing 21 over 3 + 12 over 5
a
19
b
23
c
15
d
17
e
16
f
11
8
What lowest common denominator would you use to add these fractions?
A LaTex expression showing 11 over 3 + 3 over 7
a
5
b
3
c
17
d
9
e
33
f
21