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Year 3

Add on fractions with the same denominator

I can add on fractions with the same denominator.

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New

Year 3

Add on fractions with the same denominator

I can add on fractions with the same denominator.

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Share activities with pupils

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Lesson details

Key learning points

If fractions have the same denominator they can be added on.
If 2 plus 3 is equal to 5 then 2 one sevenths plus 3 one sevenths is equal to 5 one sevenths.
To add fractions with the same denominator you use the language of unitising.

Keywords

Units - The unit is one of something that defines the ‘one’ you are counting in.
Denominator - A denominator is the bottom number in a fraction. It shows how many parts a whole has been divided into.
Numerator - A numerator is the top number in a fraction. It shows how many parts we have.

Common misconception

When adding fractions with the same denominator many children may try and add both the numerator and denominator.

This is a misunderstanding of the unitisation. Practise counting in different set of objects such as cubes, counters, children. Move children on to counting in fractions and explain that this is simply a different unit, shown by the denominator.

It might be a good idea to use a counting stick (split into tenths) and a roll of paper to draw the growth of the sunflower in the second lesson cycle so the children can see the process of adding on a fraction. Consider ways you can practically show other problems or adapt to your setting.

Teacher tip

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).

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Starter quiz

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6 Questions

Q1.

Which of these definitions describes a total?

A number added to another number.

Correct answer: All of the parts added together.

Q2.

What is the missing number in this bar model?

Correct Answer: 5, five

Q3.

What addition is being shown by this number line?

4 + 1 = 5

Correct answer: 1 + 4 = 5

4 = 5 + 1

1 = 5 + 4

Q4.

A bag of marbles contains 9 marbles. What fraction of the total is each marble?

$$ \frac{2}{8} $$

$$ \frac{1}{8} $$

Correct answer: $$ \frac{1}{9} $$

$$ \frac{2}{9} $$

Q5.

What is the missing number in this bar model?

Correct answer: 1

Q6.

What is true of the numerator and denominator of a fraction if the fraction is equivalent to one whole?

They add together to make 1

They are always both 1

Correct answer: They are the same.

Exit quiz

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6 Questions

Q1.

Look at the picture. What is the unit of this addition?

Ones

Wholes

Correct answer: Strawberries

Q2.

Look at the image. What is the missing label marked with a question mark?

Correct answer: addend

sum

part

Q3.

What addition is being represented on this number line?

$$ \frac{1}{8} $$ + $$ \frac{4}{8} $$ = $$ \frac{3}{8} $$

Correct answer: $$ \frac{1}{8} $$ + $$ \frac{3}{8} $$ = $$ \frac{4}{8} $$

$$ \frac{6}{8} $$ + $$ \frac{5}{8} $$ = $$ \frac{1}{8} $$

$$ \frac{3}{8} $$ + $$ \frac{3}{8} $$ = $$ \frac{6}{8} $$

Q4.

What is the sum of this equation? $$ \frac{2}{7} $$ + $$ \frac{4}{7} $$ = ___

$$ \frac{6}{14} $$

$$ \frac{8}{7} $$

Correct answer: $$ \frac{6}{7} $$

Q5.

What is the correct sum for this equation? ___ = $$ \frac{4}{15} $$ + $$ \frac{6}{15} $$

$$ \frac{10}{30} $$

Correct answer: $$ \frac{10}{15} $$

$$ \frac{15}{30} $$

Q6.

Which equation matches the problem? A sunflower is two-tenths of a metre tall. Over a month, it grows four-tenths more. How tall is the sunflower now?

$$ \frac{2}{10} $$ + $$ \frac{4}{10} $$ = $$ \frac{10}{10} $$

$$ \frac{2}{10} $$ + $$ \frac{6}{10} $$ = $$ \frac{4}{10} $$

Correct answer: $$ \frac{2}{10} $$ + $$ \frac{4}{10} $$ = $$ \frac{6}{10} $$