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      Checking understanding of congruence

      Lesson details

      Learning outcome

      I can translate, reflect and rotate a shape.

      Key learning points

      1. Translation, reflection and rotation produce an image congruent to the object.
      2. Translation involves moving the shape.
      3. Rotation involves turning the shape about a defined point.
      4. Reflection involves flipping the shape.

      Keywords

      • 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 find it difficult to match up corresponding measurements on two congruent shapes when they are in different orientations.

      Look lengths which are between any pairs of known angles or look for angles which are between pairs of adjacent known lengths. Also, tracing paper could be used to reflect/rotate/translate one shape onto the other.

      Teacher tip

      Pupils may find tracing paper helpful for all of the questions in the tasks.

      Licence

      This content is © Oak National Academy Limited (2026), licensed on Open Government Licence version 3.0
      except where otherwise stated. See Oak's terms & conditions
      (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

      6 Questions

      Q1.
      Match each transformation to its description.

      Correct Answer:enlargement,changing the size of an object while maintaining the same proportions

      changing the size of an object while maintaining the same proportions

      Correct Answer:reflection,flipping an object over a fixed line

      flipping an object over a fixed line

      Correct Answer:rotation,turning an object by a fixed amount and around a fixed point

      turning an object by a fixed amount and around a fixed point

      Correct Answer:translation,moving every point of an object by the same distance and direction

      moving every point of an object by the same distance and direction

      Q2.
      If one shape can fit exactly on top of another using rotation, reflection or translation, then the shapes are __________.

      alternate
      Correct answer: congruent
      corresponding
      supplementary

      Q3.
      Which properties of a triangle would remain invariant when it is rotated 90°.

      Correct answer: The lengths of its edges.
      The orientation of the shape.
      The positions of its edges.
      The positions of its vertices.
      Correct answer: The size of its angles.

      Q4.
      A square with length 5 cm is enlarged by a scale factor of 1. The length of square in the image is cm.

      Correct Answer: 5, five

      Q5.
      Which of the triangles can NOT be obtained by reflecting triangle T?

      An image in a quiz
      A
      B
      Correct answer: C
      D
      E

      Q6.
      Triangle A has been reflected over the line of reflection to create triangle B. Match each unknown length from triangle B with its size.

      An image in a quiz
      Correct Answer:$$a \text{ cm}$$,4 cm

      4 cm

      Correct Answer:$$b\text{ cm}$$,3 cm

      3 cm

      Correct Answer:$$c\text{ cm}$$,5 cm

      5 cm

      6 Questions

      Q1.
      Which shape is congruent to rectangle R?

      An image in a quiz
      A
      B
      Correct answer: C

      Q2.
      Which transformation can produce an image that is incongruent to an object?

      Correct answer: enlargement
      reflection
      rotation
      translation

      Q3.
      Which triangles are congruent to triangle T?

      An image in a quiz
      Correct answer: A
      Correct answer: B
      C
      Correct answer: D
      Correct answer: E

      Q4.
      Shapes A and B are congruent. Match each unknown length from shape B with its size.

      An image in a quiz
      Correct Answer:$$a \text{ cm}$$,26 cm

      26 cm

      Correct Answer:$$b \text{ cm}$$,30 cm

      30 cm

      Correct Answer:$$c\text{ cm}$$,10 cm

      10 cm

      Correct Answer:$$d\text{ cm}$$,34 cm

      34 cm

      Q5.
      When two shapes are congruent, which property of the shapes may differ?

      angles
      lengths
      Correct answer: orientation

      Q6.
      The type of transformation that maps shape A onto shape B is a .

      An image in a quiz
      Correct Answer: rotation

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