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Use Common Denominators to Order Fractions

In this worksheet, students will use common denominators to place fractions in ascending order of size.

'Use Common Denominators to Order Fractions' worksheet

Key stage:  KS 2

Curriculum topic:   Number: Fractions, Decimals and Percentages

Curriculum subtopic:   Compare and Order Fractions

Difficulty level:  

Worksheet Overview

Before we compare fractions, they need the same denominators.

We do this by using lowest common multiples.

 

Suppose we wish to compare:

 

7  and  4
9 6

 

We look for the smallest number that 9 and 6 go into.

This will be 18, so we want to change both fractions into 18ths.

 

We multiply the numerator and the denominator of 7/9 by 2:

 

7  =  14
9 18

 

We multiply the numerator and the denominator of 4/6 by 3:

 

4  =  12
6 18

 

So we now have:

 

14  and  12
18 18

 

14  >  12
18 18

 

7   4
9 6

 

 

Example

Place these fractions in ascending order of size.

 

5    1    2
8 2 3

 

Answer

The lowest common multiple of 8, 2 and 3 is 24, because 3 × 8 = 24 and 12 × 2 = 24 and 8 × 3 = 24.

We multiply the numerator and the denominator of 5/8 by 3:

 

5  =  15
8 24

 

We multiply the numerator and the denominator of 1/2 by 12:

 

1  =  12
2 24

 

We multiply the numerator and the denominator of 2/3 by 8:

 

2  =  16
3 24

 

12  <  15  <  16
24 24 24

 

So the ascending order is:

 

1    5    2
2 8 3

 

 

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