Year 3 - Maths
Add and subtract fractions with the same denominator in a range of contexts
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 and subtract fractions with the same denominator in a range of contexts.
Key Notes
- If fractions have the same denominator they can be added or subtracted.
- Number lines can represent addition and subtraction of fractions with the same denominator.
- When you add or subtract fractions with the same denominator you add or subtract the numerators.
Vocabulary To Learn
- Minuend: The minuend is the number being subtracted from.
- Subtrahend: A subtrahend is a number subtracted from another. There can be more than one.
- Numerator: A numerator is the top number in a fraction. It shows how many parts we have.
- Denominator: A denominator is the bottom number in a fraction. It shows how many parts a whole has been divided into.
Common Mistakes To Avoid
- Children might still try to add or subtract the denominators as well due to a misunderstanding about the denominator showing what unit-fraction is being used for calculation.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
If fractions have the same denominator they can be added or subtracted. Number lines can represent addition and subtraction of fractions with the same denominator.
2. Use this key word in a maths sentence and explain it clearly. 'Minuend'
The minuend is the number being subtracted from. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Children might still try to add or subtract the denominators as well due to a misunderstanding about the denominator showing what unit-fraction is being used for calculation. Correction: By this stage, buddy checking can be useful. Get the children to check each other periodically but ensure that children can also explain why this is incorrect.
More Lessons In This Unit
- Add fractions with the same denominator Study Guide
- Add fractions with the same denominator and generalise the rule 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.