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Subtracting Fractions

In this worksheet, students subtract two simple fractions by first finding their lowest common denominator.

'Subtracting Fractions' worksheet

Key stage:  KS 3

Curriculum topic:   Number

Curriculum subtopic:   Use Four Operations for All Numbers

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

When we subtract two fractions, they must have the same denominator.

We use equivalent fractions to change them into two fractions with the same lowest common denominator.

 

Example

Work out

5 - 5
6 9

 

Answer

We must first find the lowest common multiple of 6 and 9, which is 18.

Then we change each fraction into 18ths.

18 ÷ 6 = 3 so we multiply top and bottom of the first fraction by 3.

18 ÷ 9 = 2 so we multiply top and bottom of the second fraction by 2.

 

5 - 5
6 9

 

= 5 x 3 - 5 x 2
6 x 3  9 x 2

 

= 15 - 10
18  18

 

= 5
18

 

Work out

 

2 - 1
3 5

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

2 - 1
3 4

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

2 - 1
5 3

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

2 - 1
5 4

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

3 - 1
5 6

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

2 - 1
5 10

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

2 - 1
7 4

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

3 - 2
4 9

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

2 - 1
9 6

 

(Write your answer in its lowest terms in the form a/b)

Work out

 

5 - 2
6 9

 

(Write your answer in its lowest terms in the form a/b)

  • Question 1

Work out

 

2 - 1
3 5

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
7/15
EDDIE SAYS
The LCM of 3 and 5 is 15 If we convert the two fractions to both have the denominator of 15, we get; 10/15 - 3/15
  • Question 2

Work out

 

2 - 1
3 4

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
5/12
EDDIE SAYS
The LCM of 3 and 4 is 12 If we convert the two fractions to both have the denominator of 12, we get; 8/12 - 3/12
  • Question 3

Work out

 

2 - 1
5 3

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
1/15
EDDIE SAYS
The LCM of 3 and 5 is 15 If we convert the two fractions to both have the denominator of 15, we get; 6/15 - 5/15
  • Question 4

Work out

 

2 - 1
5 4

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
3/20
EDDIE SAYS
The LCM of 5 and 4 is 20 If we convert the two fractions to both have the denominator of 20, we get; 8/20 - 5/20
  • Question 5

Work out

 

3 - 1
5 6

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
13/30
EDDIE SAYS
The LCM of 5 and 6 is 30 If we convert the two fractions to both have the denominator of 30, we get; 18/30 - 5/30
  • Question 6

Work out

 

2 - 1
5 10

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
3/10
EDDIE SAYS
The LCM of 5 and 10 is 10 If we convert the two fractions to both have the denominator of 10, we get; 4/10 - 1/10
  • Question 7

Work out

 

2 - 1
7 4

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
1/28
EDDIE SAYS
The LCM of 7 and 4 is 28 If we convert the two fractions to both have the denominator of 28, we get; 8/28 - 7/28
  • Question 8

Work out

 

3 - 2
4 9

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
19/36
EDDIE SAYS
The LCM of 4 and 9 is 36 If we convert the two fractions to both have the denominator of 36, we get; 27/36 - 8/36
  • Question 9

Work out

 

2 - 1
9 6

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
1/18
EDDIE SAYS
The LCM of 9 and 6 is 18 If we convert the two fractions to both have the denominator of 18, we get; 4/18 - 3/18
  • Question 10

Work out

 

5 - 2
6 9

 

(Write your answer in its lowest terms in the form a/b)

CORRECT ANSWER
11/18
EDDIE SAYS
The LCM of 6 and 9 is 18 If we convert the two fractions to both have the denominator of 18, we get; 15/18 - 4/18
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