  # Add and Subtract Fractions with Different Denominators

In this worksheet, students practise adding and subtracting more complex fractions. Key stage:  KS 3

Curriculum topic:   Number

Curriculum subtopic:   Use Four Operations for All Numbers

Difficulty level:   #### Worksheet Overview

Example

When adding or subtracting fractions we begin by finding the lowest common multiple (LCM) of both denominators.

First find the LCM of 24 and 15.

 24 48 96 120 ... 15 30 45 60 75 90 105 120 ...

The LCM is 120.

120 = 5 x 24

and

120 = 8 x 15

 19 - 8 = 19 x 5 - 8 x 8 = 95 - 64 = 31 24 15 24 x 5 15 x 8 120 120

Answers in this worksheet should be given as reduced fractions, written with a / sign, e.g. 7/18

Leave fractions as top-heavy, but write integers as whole numbers (i.e. 5 not 5/1)

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