# Use knowledge of adding and subtracting related unit fractions to solve problems

I can use knowledge of adding and subtracting related unit fractions to solve problems.

# Use knowledge of adding and subtracting related unit fractions to solve problems

I can use knowledge of adding and subtracting related unit fractions to solve problems.

## Lesson details

### Key learning points

- When adding and subtracting fractions with the same denominators you just add or subtract the numerators.
- Common multiples help you to convert a fraction to a common denominator.
- The language of unitising helps you to add and subtract fractions with the same denominators.
- When adding and subtracting fractions with the same denominators you just add the numerators.

### Common misconception

Pupils compare expressions by only ever calculating the value of each expression before comparing.

Encourage pupils to consider the magnitude of the fractions they are adding or subtracting. Comparing fractions to one-half is an effective way to help identify their magnitude and whether then expression would be larger or smaller.

### Keywords

Related fractions - When the denominator of one fraction is a multiple of the denominator of another fraction, we can say these fractions are related fractions.

Common denominator - When two or more fractions share the same denominator, you can say they have a common denominator.

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Video

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## Starter quiz

### 6 Questions

## Exit quiz

### 6 Questions

$$ {1} \over {4}$$ -

$$ {9} \over {4}$$

$$ {1} \over {12}$$ -

$$ {4} \over {12}$$

$$ {1} \over {9}$$ -

$$ {5} \over {9}$$

$$ {5} \over {3}$$ -

$$ {12} \over {3}$$