# Subtracting Fractions

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

Key stage:  KS 3

Curriculum topic:   Number

Curriculum subtopic:   Use Four Operations for All Numbers

Difficulty level:

### 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

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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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