Scale factor in similar triangles
The scale factor is the number by which one similar triangle is enlarged or reduced to get the other.
Practice This ConceptMain explanation
Teacher explanation
Scale factor shows the size change between similar triangles. If the factor is k, then each corresponding side is multiplied by k, while area changes by k².
Example
If a triangle is enlarged by scale factor 3, a 4 cm side becomes 12 cm.
Simple analogy
Sides by k, areas by k².
Common confusion
Students sometimes reverse the factor or use it directly for area without squaring.
Exam tip
Decide first whether you are moving from the smaller triangle to the larger one or the other way around.
Answer writing and exam use
1-mark use
Write the exact meaning of scale factor in similar triangles in one clean line.
2-mark use
Define scale factor in similar triangles and add one example or condition.
3-mark use
Explain scale factor in similar triangles, show the method or example, and mention the common mistake.
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