Pythagoras, Similarity And Congruence
Overview
Three ideas do most of the heavy lifting in 4MB1 geometry: a right-angled triangle's sides obey a fixed relationship, enlarged shapes scale their area and volume in predictable ways, and two triangles can be proved identical using surprisingly little information. This topic ties all three together, because a similarity or congruence argument almost always ends with a Pythagoras calculation, or starts from one.
You will extend Pythagoras' theorem from flat diagrams into three-dimensional solids, learn why area scales by the square of the length scale factor and volume by its cube, and work through each of the four ways Edexcel accepts as proof that two triangles are congruent: SSS, SAS, ASA and RHS. Knowing exactly which condition applies, and being able to write the proof out fully, is worth real marks on both papers.
Objectives
- Use Pythagoras' theorem in 2D and 3D
- Understand and use similarity, including how scale factors relate to areas and volumes of similar figures
- Prove the similarity of two triangles
- Understand and identify congruent shapes
- Use SSS, SAS, ASA and RHS conditions to prove the congruence of triangles
Mind map
This topic is mapped out so you can see how the ideas connect.
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Flashcards
Quick recall practice on the facts this topic is tested on.
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Pythagoras, Similarity And Congruence. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- A right-angled triangle has shorter sides of 6 cm and 8 cm. What is the length of the hypotenuse? A) 7 cm B) 10 cm C) 14 cm D) 48 cm Answer: B
- A cuboid has edges 2 cm, 3 cm and 6 cm. What is the length of its space diagonal? A) 6 cm B) 7 cm C) 11 cm D) 49 cm Answer: B
- Two similar solids have a linear scale factor of 3. By what factor does the volume of the larger solid exceed the smaller? A) 3 B) 6 C) 9 D) 27 Answer: D
- Which condition CANNOT be used on its own to prove two triangles are congruent? A) SSS B) SAS C) SSA (side, side, non-included angle) D) RHS Answer: C
- Two right-angled triangles have equal hypotenuses and one further pair of equal corresponding sides. Which congruence condition proves they are congruent? A) AAS B) SSA C) RHS D) AA Answer: C
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Practice Mock Questions
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