Similarity & Congruence

Work with similar and congruent triangles: scale factors, missing sides and area ratios, with the reason (AA, SAS, SSS) given. Try “two similar triangles have sides 6 and 9; area ratio?”.

Try an example:

How the Similarity & Congruence works

  1. Match corresponding sides and confirm similarity (AA, SAS or SSS).
  2. Find the scale factor k = 9 ÷ 6 = 1.5.
  3. Lengths scale by k, areas by k² (2.25) and volumes by k³.

Frequently asked questions

What is the difference between similar and congruent?

Congruent shapes are identical in size and shape. Similar shapes have the same shape but can differ in size.

How does scale factor affect area?

Area scales by the square of the scale factor.

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