high importancemedium8 min

Similarity of triangles

Two triangles are similar when their corresponding angles are equal and their corresponding sides are in the same ratio.

Practice This Concept

Main explanation

Teacher explanation

Similarity means the triangles have the same shape, even if one is larger or smaller. The angle pattern stays the same, and every matching side changes by a fixed scale factor.

Example

Triangles with sides 3 cm, 4 cm, 5 cm and 6 cm, 8 cm, 10 cm are similar because each matching side is in the ratio 1:2.

Simple analogy

Same shape, different size.

Common confusion

Students often think similar triangles must have equal side lengths. That is congruence, not similarity.

Exam tip

Write the corresponding vertices in the same order before checking angles or side ratios.

Study the similarity of triangles diagram carefully

Use the labelled diagram to keep similarity of triangles clear in short answers and revision.

What this diagram makes clear

This diagram keeps the labels and direction of similarity of triangles in the right order.

Where this helps in exams

Use this for labelled diagram work and short exam answers on similarity of triangles.

Revision cue

Revise similarity of triangles through the labels before writing the answer.

Answer writing and exam use

1-mark use

Write the exact meaning of similarity of triangles in one clean line.

2-mark use

Define similarity of triangles and add one example or condition.

3-mark use

Explain similarity of triangles, show the method or example, and mention the common mistake.

MCQ Quiz

Practice this concept with focused MCQs

Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.

10 MCQs5 MinutesInstant Results