Choose exam board for KS4 Computer Science (GCSE)
Choose exam board for KS4 English
Choose exam board for KS4 French
Choose exam board for KS4 Geography
Choose exam board for KS4 German
Choose exam board for KS4 History
Choose tier for KS4 Maths
Choose exam board for KS4 Music
Choose exam board for KS4 Physical education (GCSE)
Choose exam board for KS4 Religious education (GCSE)
Choose exam board for KS4 Spanish

      Add fractions with the same denominator and generalise the rule

      Lesson details

      Learning outcome

      I can add fractions with the same denominator and generalise the rule.

      Key learning points

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

      Keywords

      • Generalisation - A generalisation is a statement or rule that applies correctly to all relevant cases.

      • 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

      In the addition of fractions, many children will try to add together both the numerator and denominator.

      Show the children many completed examples using representations alongside the fraction notation. Encourage them to make generalisations and spot that the denominator remains the same because it is the unit.

      Teacher tip

      Encourage discussion here. Generalisation shouldn't just be waiting until the teacher gives the answer. Use your learning wall if available to record thoughts, observations and then the final generalisation.

      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

      Loading...

      Prior knowledge starter quiz

      6 Questions

      Q1.
      Which of these definitions describes the sum?

      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: 2, two

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

      An image in a quiz
      10 = 50 + 40
      40 + 10 = 50
      Correct answer: 10 + 40 = 50
      40 = 50 + 10

      Q4.
      Each marble in a bag is $$ \frac{1}{9} $$ of the whole bag. How many marbles are there in the bag?

      1
      10
      Correct answer: 9
      12

      Q5.
      What is the missing fraction in this bar model?

      An image in a quiz
      $$ \frac{1}{3} $$
      $$ \frac{1}{4} $$
      Correct answer: $$ \frac{1}{5} $$
      $$ \frac{1}{6} $$

      Q6.
      Select the correct sum. $$ \frac{2}{7} $$ + $$ \frac{4}{7} $$ = ___

      Correct answer: $$ \frac{6}{7} $$
      $$ \frac{7}{6} $$
      $$ \frac{6}{14} $$
      $$ \frac{8}{14} $$

      6 Questions

      Q1.
      Look at the image. What is the missing label marked with a question mark?

      An image in a quiz
      addend
      Correct answer: sum
      part

      Q2.
      Look at the number line. The missing addend is ___

      An image in a quiz
      $$ \frac{1}{10} $$
      Correct answer: $$ \frac{2}{10} $$
      $$ \frac{3}{10} $$
      $$ \frac{5}{10} $$

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

      An image in a quiz
      $$ \frac{1}{8} $$ + $$ \frac{4}{8} $$ = $$ \frac{3}{8} $$
      $$ \frac{6}{8} $$ + $$ \frac{5}{8} $$ = $$ \frac{1}{8} $$
      $$ \frac{3}{8} $$ + $$ \frac{3}{8} $$ = $$ \frac{6}{8} $$
      Correct answer: $$ \frac{1}{8} $$ + $$ \frac{3}{8} $$ = $$ \frac{4}{8} $$

      Q4.
      What is the sum of this equation? $$ \frac{3}{7} $$ + $$ \frac{2}{7} $$ + $$ \frac{1}{7} $$ = ___

      $$ \frac{6}{14} $$
      $$ \frac{8}{7} $$
      Correct answer: $$ \frac{6}{7} $$

      Q5.
      What is the correct sum for this equation? ___ = $$ \frac{4}{20} $$ + $$ \frac{6}{20} $$+ $$ \frac{6}{20} $$

      Correct answer: $$ \frac{16}{20} $$
      $$ \frac{10}{20} $$
      $$ \frac{15}{60} $$

      Q6.
      Which of the following numbers could be used to complete this inequality?

      An image in a quiz
      Correct answer: 1
      Correct answer: 2
      3
      4

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