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      Add on fractions with the same denominator

      Lesson details

      Learning outcome

      I can add on fractions with the same denominator.

      Key learning points

      1. If fractions have the same denominator they can be added on.
      2. If 2 plus 3 is equal to 5 then 2 one sevenths plus 3 one sevenths is equal to 5 one sevenths.
      3. 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.

      Teacher tip

      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.

      Licence

      This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0
      except where otherwise stated. See Oak's terms & conditions
      (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

      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?

      An image in a quiz
      Correct Answer: 5, five

      Q3.
      What addition is being shown by this number line?

      An image in a quiz
      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?

      An image in a quiz
      Correct answer: 1
      5
      6

      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.

      6 Questions

      Q1.
      Look at the picture. What is the unit of this addition?

      An image in a quiz
      Ones
      Wholes
      Correct answer: Strawberries

      Q2.
      Look at the image. What is the missing label marked with a question mark?

      An image in a quiz
      Correct answer: addend
      sum
      part

      Q3.
      What addition is being represented on this number line?

      An image in a quiz
      $$ \frac{1}{8} $$ + $$ \frac{4}{8} $$ = $$ \frac{3}{8} $$
      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: $$ \frac{2}{10} $$ + $$ \frac{4}{10} $$ = $$ \frac{6}{10} $$

      To help you plan your 3 maths lesson on: Add on fractions with the same denominator, download all teaching resources for free and adapt to suit your pupils' needs...