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GCSE Maths: Congruence & Similarity

Congruent shapes are identical; similar shapes are the same shape at a different size, linked by a scale factor. Adaptive practice for AQA, Edexcel, OCR and Eduqas.

GeometryFoundation & HigherAQA · Edexcel · OCR · Eduqas

What you need to know

The concepts examiners test on congruence & similarity, and what each one is really asking.

Decide whether two shapes are congruent, similar, or neither
Name the condition (SSS, SAS, ASA, RHS) that proves two triangles congruent
Find the scale factor between two similar shapes
Use the scale factor to calculate a missing length

Where marks get lost

The exam technique that separates a correct method from a correct answer.

  • Using AAA as a congruence condition — it only proves similarity
  • Dividing lengths that are not corresponding sides
  • Getting the scale factor upside down and shrinking when you should enlarge
  • Proving congruence but not naming the condition, which is where the mark is

Congruence & Similarity questions students ask

Is Congruence & Similarity on the Foundation paper?

Yes. Congruence & Similarity appears at both Foundation and Higher tier, though Higher papers take it further.

What should I know before starting Congruence & Similarity?

It builds on Properties of 2D Shapes and Ratio and Proportion. If those feel shaky, practise them first — Congruence & Similarity questions assume them.

What is the most common mistake in Congruence & Similarity?

Using AAA as a congruence condition — it only proves similarity.

Which exam boards cover Congruence & Similarity?

All four we support — AQA, Edexcel, OCR and Eduqas. GCSE Maths subject content is set by the DfE, so the topic is common to every board; what changes is the paper structure and the grade boundaries.