Myths about teaching can hold you back
- Year 10•
- Higher
Checking and securing understanding of congruence and similarity
I can identify (by eye) which shapes are congruent, similar or neither.
- Year 10•
- Higher
Checking and securing understanding of congruence and similarity
I can identify (by eye) which shapes are congruent, similar or neither.
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Lesson details
Key learning points
- If two shapes are congruent, then they are similar.
- A ratio table can be a helpful tool for checking the multipliers.
- The multiplicative relationship between the sides of the object is preserved in its image.
- It can be easier to determine (by eye) which shapes are NOT congruent or similar.
Keywords
Similar - Two shapes are similar if the only difference between them is their size. Their side lengths are in the same proportions.
Congruent - If one shape can fit exactly on top of another using rotation, reflection or translation, then the shapes are congruent.
Object - The object is the starting figure, before a transformation has been applied.
Image - The image is the resulting figure, after a transformation has been applied.
Invariant - A property of a shape is invariant if that property has not changed after the shape is transformed.
Common misconception
Congruent shapes are not similar shapes.
Congruent shapes are similar shapes. The scale factor, or multiplier, between them is one.
To help you plan your year 10 maths lesson on: Checking and securing understanding of congruence and similarity, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 10 maths lesson on: Checking and securing understanding of congruence and similarity, 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 4 maths lessons from the Further transformations unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
Licence
Prior knowledge starter quiz
6 Questions
Q1.A property of a shape is __________ if that property has not changed after the shape is transformed.
Q2.When an object is transformed the resulting shape is called the .
Q3.The size of the missing angle in this quadrilateral is °.

Q4.Select the transformations that will always produce an image that is congruent to the object.
Q5.What are the lengths of the sides that are adjacent to the angle of 80° in this quadrilateral?

Q6.Rectangle B is an enlargement of rectangle A by scale factor 2. Rectangle A has perimeter = 16 cm and area = 15 cm². Both rectangles have integer side lengths. Find the area and perimeter of B.

Assessment exit quiz
6 Questions
Q1.Two shapes are if the only difference between them is their size. Their side lengths are in the same proportions.
Q2.If one shape can fit exactly on top of another using rotation, reflection or translation, then the shapes are .
Q3.Select the transformations that will always produce an image that is congruent to the object.
Q4.Some Oak pupils discuss whether shapes A and B are congruent or similar. Who is correct?

Q5.Shapes A and B are congruent. What is the length of the side marked $$x$$?

Q6.Quadrilaterals A and B are similar. The length of the side marked $$x$$ is cm.
