Myths about teaching can hold you back
- Year 9
Congruent, similar or neither
I can differentiate between shapes which are congruent or similar or neither.
- Year 9
Congruent, similar or neither
I can differentiate between shapes which are congruent or similar or neither.
Lesson details
Key learning points
- If two shapes are congruent, then they are similar.
- Congruent shapes have a scalar of one.
- 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.
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.
Common misconception
Pupils may mix up the meanings of congruence and similarity or struggle with the hierarchy of their nested sets (e.g. thinking that all similar shapes are congruent rather than the other way around).
Frequently refer to a Venn diagram showing the set of congruence shapes inside the set of similar shapes when examining pairs of shapes.
To help you plan your year 9 maths lesson on: Congruent, similar or neither, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 9 maths lesson on: Congruent, similar or neither, 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 3 maths lessons from the Geometrical properties: similarity and Pythagoras' theorem unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
Licence
Prior knowledge starter quiz
6 Questions
Q1.Which triangle is congruent to triangle T?

Q2.Which triangle is similar to triangle T, but not congruent to triangle T?

Q3.Rectangle A has lengths 3 cm by 6 cm. Rectangle B is congruent to rectangle A. One of the lengths of rectangle B is 6 cm, so the other length is cm.
Q4.The image shows two congruent pentagons. What is the value of $$x$$?

Q5.The image shows two similar hexagons. The size of the angle $$x°$$ is °.

Q6.Rectangle A has lengths 3 cm by 6 cm. Rectangle B is similar, but not congruent, to rectangle A. One of the lengths of rectangle B is 6 cm, so the other length is cm.
Assessment exit quiz
6 Questions
Q1.The two shapes in the image are __________.

Q2.The two shapes in the image are __________.

Q3.The two shapes in the image are __________.

Q4.∆ABG and ∆ADE are __________.

Q5.∆ADE and ∆ACF are __________.

Q6.∆ABC and ∆CDE are __________.
