Similar shapes
Objective. Use a scale factor to find missing lengths in similar shapes.
- 1. Learn
- 2. Worked example
- 3. Practice
- 4. Feedback
- 5. Continue
Learn: the key idea
Similar shapes have equal angles and lengths in the same ratio. Find the scale factor from a matching pair of sides, then apply it.
Worked example
Two similar triangles: sides 3 cm and 12 cm match. Another side is 5 cm. Its pair?
- 1Scale factor: 12 ÷ 3 = 4.
- 25 × 4 = 20.
Answer: 20 cm
Concept mastery
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Complete a practice set to see your concept breakdown here.
Practice
Practice happens on its own screen, one question at a time. Answers stay hidden until you submit yours, and you can stop and pick up at the same question later.
Start practisingCommon mistake. Adding a constant difference instead of multiplying by a scale factor.
Your progress
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