Describe the relationship between scale factors and perimeters of two shapes
Lesson details
Learning outcome
I can describe the relationship between scale factors and side lengths and perimeters of two shapes.
Key learning points
- If the lengths of the sides of a shape have been doubled, the perimeter will be double.
- If the side lengths of a shape are multiplied by the same factor the perimeter will be multiplied by the same factor.
- The number which all the sides have been multiplied by is called a scale factor.
Keywords
Perimeter - Perimeter is the distance around a two-dimensional shape.
Scale factor - A scale factor is the multiplier between similar shapes that describes how large one shape is compared to the other.
Similar - Two shapes are similar when one shape can become the other after a resize, flip, slide or turn.
Common misconception
Pupils may remember to scale one of the sides (or pairs of sides) of a shape but forget to scale the others.
Focus attention on what it means when a shape is similar, drawing on examples and non-examples to support learners to understand how scaling affects all side lengths.
Teacher tip
Providing to-scale examples of scaled polygons initially may support all learners to practically see and measure the scaling that has taken place.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Double 17 is
Q2.Multiply 16 by 4
Q3.Which of these is the same as dividing by two?
Q4.Match the words to their correct definitions.
Change something
Make something larger
Make something smaller
Q5.Match the equations to the correct product.
30
28
24
27
Q6.Which of the following are multiples of 7?
Assessment exit quiz
6 Questions
Q1.Select all of the scale factors where the result would be a shape with a greater length and width than the original.
Q2.Shape A is a square with a side length of 3 cm and Shape B is a square with a side length of 12 cm. Shape A has been scaled by a scale factor of to create Shape B.
Q3.Shape A is an equilateral triangle with a side length of 3 cm and Shape B is an equilateral triangle with a side length of 9 cm. Shape A has been scaled by a scale factor of to create Shape B.
Q4.Shape A is a square with a side length of 3 cm which has been scaled by a scale factor of 3 to get Shape B. What is the perimeter of Shape B? cm.
Q5.Shape A is a triangle with a side length of 3 cm which has been scaled by a scale factor of 4 to get Shape B. What is the perimeter of Shape B? cm.
Q6.Select all of the scale factors where the result would be a shape with a smaller length and width than the original.
To help you plan your 6 maths lesson on: Describe the relationship between scale factors and perimeters of two shapes, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 6 maths lesson on: Describe the relationship between scale factors and perimeters of two shapes, 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 Area, perimeter, position and direction unit, dive into the full primary maths curriculum, or learn more about lesson planning.