Year 3 - Maths
Substitute a fraction representing a whole to solve subtraction problems
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 substitute a fraction representing a whole to solve subtraction problems.
Key Notes
- A fraction with the same numerator and denominator is equal to one whole.
- To subtract a fraction from a whole, convert the whole to a fraction with the same denominator as the subtrahend.
- All fractions where the numerator and denominator are the same are equal and equal to 1
Vocabulary To Learn
- Substitute: Substitute means to put in place of another and it can be used to replace a fraction with another fraction of equal value.
- Expression: An expression contains one or more values, where each value is separated by an operator.
Common Mistakes To Avoid
- Children might struggle with the idea that two fractions, each with the same numerator and denominator but different numbers, can be equivalent. For example, four-fourths is equal to ten-tenths.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
A fraction with the same numerator and denominator is equal to one whole. To subtract a fraction from a whole, convert the whole to a fraction with the same denominator as the subtrahend.
2. Use this key word in a maths sentence and explain it clearly. 'Substitute'
Substitute means to put in place of another and it can be used to replace a fraction with another fraction of equal value. 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 struggle with the idea that two fractions, each with the same numerator and denominator but different numbers, can be equivalent. For example, four-fourths is equal to ten-tenths. Correction: Use a fraction wall to help with this. Compare the rows and establish that the whole is the same so they are equivalent. Ask the children to list as many as they can which will help build confidence.
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 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
- 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.