Maths KS2: Adding and subtracting fractions

Amongst the ruins of an ancient city, Olivia and Hassan learn how to add and subtract fractions.

Archimedes explains how to perform subtraction using the fractions of the ruins and compiling them together, and with this new knowledge they're able to create a beautiful statue of Hypatia, before moving onto the next part of the mathematical maze.

This short animated film is from the BBC Teach series, Hyaptia's Mathematical Maze.

Teacher Notes

Before watching the film

Prior to this lesson you may wish to introduce students to other relevant topics, for example:

  • Common factors
  • Common multiples
  • Equivalent fractions and converting

During watching the film

Depending on your lesson’s focus, you may wish to pause the film at certain points to check for understanding by asking questions such as:

  • What are the rules for adding and subtracting fractions?
  • Why do we add and subtract the numerators but not the denominators?

Final question:
A chariot travels from the temple to the outpost. In the morning, it completes ²⁄₃ of the journey. In the afternoon, it completes ¹⁄₅ of the journey.

What fraction of the journey has been completed altogether? What fraction of the journey is left to travel?

Answer to the final question:
Completed: ¹⁰⁄₁₅ + 3⁄₁₅ = 13⁄₁₅ Left to travel: ²⁄₁₅

Following on from the film:

  • Add fractions using bar models of the relative size.
  • Explore subtraction as difference by giving an open-ended question, e.g. I am thinking of two fractions. They have a difference of ¹⁄₂. What might my fractions be? I.e. ³⁄₈ and ⁷⁄₈. 2⁄₁₀ and ⁷⁄₁₀.
  • In these examples, can the denominator ever be an odd number?

Curriculum Notes

This short film is suitable for teaching maths at KS2 in England, Wales and Northern Ireland and 2nd Level in Scotland.

More from Hypatia's Mathematical Maze

Adding and subtracting using mental methods
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Adding and subtracting using written methods
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How and why we round numbers
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Using addition and subtraction in multi-step problems
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Multiplying by 10, 100 and 1000
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Mental multiplication
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Factors, multiples and primes
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Multiplying using written methods
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Dividing using written methods
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Recognising and comparing fractions
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Multiplying and dividing fractions
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