Congruence in shapes

I can recognise that for congruent shapes both side lengths and angle sizes are preserved.

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Year 9

Congruence in shapes

I can recognise that for congruent shapes both side lengths and angle sizes are preserved.

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Lesson details

Key learning points

Two shapes are not congruent if there is a pair of lengths with a scalar not equal to one.
Congruent does not mean the orientation must be the same.
The angle sizes do not change.

Common misconception

Pupils may think that they do not have enough information about a shape to determine whether it is congruent to another shape, when in fact they do.

Pupils could attempt the draw the shape based on the information that they have. They can then consider whether there are multiple way that the shape can be drawn while still satisfying all the given information.

Keywords

Congruent - If one shape can fit exactly on top of another using rotation, reflection or translation, then the shapes are congruent.
Co-interior angles - Co-interior angles are on the same side of the transversal line and in between the two other lines.

In Task B, pupils could check whether the shapes they make are congruent by cutting them out and then placing one on top of the other.

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