Year 5 - Maths
Calculate the area of shapes made from 2 rectangles by decomposing the shape in different ways
Link area of rectangles to multiplication
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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 calculate the area of a rectangle using multiplication and use their knowledge of area to solve problems.
Lesson Summary
You can decompose or split shapes into rectangles in different ways.
Key Notes
- Different ways of decomposing the shape will give the same answer.
- The area stays the same however you split the shape.
- Calculate the areas of the rectangular parts and recombine to find the area of the whole shape.
Vocabulary To Learn
- Rectilinear: A shape made up of two or more rectangles is known as rectilinear.
- Compound: A compound shape is one made up of two or more shapes.
Common Mistakes To Avoid
- Some pupils may not see that two rectilinear shapes can look very different but have the same area.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Different ways of decomposing the shape will give the same answer. The area stays the same however you split the shape.
2. Use this key word in a maths sentence and explain it clearly. 'Rectilinear'
A shape made up of two or more rectangles is known as rectilinear. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Some pupils may not see that two rectilinear shapes can look very different but have the same area. Correction: Cut out a large rectangle. Cut it into two rectangles. Ask pupils to move one of the rectangles and reposition it. Has the area changed?
More Lessons In This Unit
- Calculate missing dimensions in rectangles and compound rectilinear shapes Study Guide
- Calculate the area of compound rectilinear shapes Study Guide
- Calculate the area of shapes made from 2 or more rectangles Study Guide
- Calculate the areas of rectangles using multiplication Study Guide
- Choose an efficient way to decompose a compound shape to calculate the area Study Guide
- Explain how to calculate the area of a rectangle using multiplication Study Guide
- Measure the area of flat shapes using square centimetres Study Guide
- Measure the area of flat shapes using square metres Study Guide
- Use knowledge of area to solve problems in a range of contexts Study Guide
Browse all guides in the Year 5 Maths guide library.