Calculate the area of shapes made from 2 rectangles by decomposing the shape in different ways
Lesson details
Learning outcome
You can decompose or split shapes into rectangles in different ways.
Key learning points
- 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.
Keywords
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 misconception
Some pupils may not see that two rectilinear shapes can look very different but have the same area.
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?
Teacher tip
Some pupils may need extra practice with working out the area of compound shapes where the rectangles are not pre-marked before they move onto example requiring them to divide the shape into rectangles.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.To calculate the of a rectangle, multiply the length by the width.
Q2.What is the area of this square? cm².
Q3.Calculate the area of this rectangle. A = cm².
Q4.What is the area of the lawn if the sides measure 13 m and 9 m?
Q5.A picture is put into a frame that is 17cm long and 8 cm wide. What is the area of the glass in the frame? cm².
Q6.The school hall measures 25 m by 9 m. What is the area of the hall floor? m².
Assessment exit quiz
6 Questions
Q1.Match the start and end of the sentences to describe the shapes correctly.
has all angles made from right angles.
is made up of two or more shapes.
Q2.Which times tables facts are needed to calculate the area of the shape?
Q3.Which times tables facts are needed to calculate the area of the shape?
Q4.True or false. These rectilinear shapes show the same area.
Q5.Calculate the area of this rectilinear shape. m²
Q6.Calculate the area of this rectilinear shape. m²
To help you plan your 5 maths lesson on: Calculate the area of shapes made from 2 rectangles by decomposing the shape in different ways, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 5 maths lesson on: Calculate the area of shapes made from 2 rectangles by decomposing the shape in different ways, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 2 maths lessons from the Link area of rectangles to multiplication unit, dive into the full primary maths curriculum, or learn more about lesson planning.