Year 3 - Maths
Add fractions with the same denominator and generalise the rule
Composition of non-unit fractions: addition and subtraction
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will use repeated addition of a unit fraction to form a non-unit fraction. They will compare non-unit fractions with the same denominator. They will add and subtract fractions with the same denominator.
Lesson Summary
You will learn to add fractions with the same denominator and generalise the rule.
Key Notes
- To add fractions with the same denominator you add the numerators using the language of unitising.
- If 2 plus 3 is equal to 5 then 2 one sevenths plus 3 one sevenths is equal to 5 one sevenths.
- If fractions have the same denominator they can be added.
Vocabulary To Learn
- 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 Mistakes To Avoid
- In the addition of fractions, many children will try to add together both the numerator and denominator.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
To add fractions with the same denominator you add the numerators using the language of unitising. If 2 plus 3 is equal to 5 then 2 one sevenths plus 3 one sevenths is equal to 5 one sevenths.
2. Use this key word in a maths sentence and explain it clearly. 'Generalisation'
A generalisation is a statement or rule that applies correctly to all relevant cases. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: In the addition of fractions, many children will try to add together both the numerator and denominator. Correction: 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.
More Lessons In This Unit
- Add and subtract fractions with the same denominator in a range of contexts Study Guide
- Add fractions with the same denominator Study Guide
- Add on fractions with the same denominator Study Guide
- Explain that addition and subtraction of fractions are inverse operations Study Guide
- Substitute a fraction representing a whole to solve subtraction problems Study Guide
- Subtract fractions from a whole by converting the whole to a fraction Study Guide
- Subtract fractions with the same denominator Study Guide
- Use repeated addition of a unit fraction to form 1 Study Guide
- Use repeated addition of a unit fraction to form a non-unit fraction Study Guide
Browse all guides in the Year 3 Maths guide library.