Invalid Conditions — Common Traps
Part of Congruence · GCSE GCSE Mathematics revision
This exam tips covers Invalid Conditions — Common Traps within Congruence for GCSE Mathematics. Revise Congruence in Geometry & Measures for GCSE Mathematics with 15 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 4 of 11 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 4 of 11
Practice
15 questions
Recall
12 flashcards
Invalid Conditions — Common Traps
- AAA (Angle-Angle-Angle) is NOT sufficient for congruence. Three equal angles gives similar triangles, but they could be any size.
- SSA (or ASS) is NOT a valid congruence condition. Two sides and a non-included angle can produce two different triangles (the ambiguous case).
- In SAS, the angle must be between the two sides — it is not enough for any angle to be equal.
- RHS only works when you know there is a right angle — you cannot assume it.
Keep building this topic
Read this section alongside the surrounding pages in Congruence. That gives you the full topic sequence instead of a single isolated revision point.
Practice Questions for Congruence
Which of the following is NOT a valid congruence condition for triangles?
When writing a congruence statement, such as triangle ABC ≅ triangle PQR, explain what it tells you about the sides and angles of the two triangles.
Quick Recall Flashcards
15 questions on Congruence — practise free
Instant marking, adaptive difficulty, and 12 spaced repetition flashcards. Free until your GCSEs.
Try PrepWise Free