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