Geometry and TrigonometryHardPerimeter of a scaled right triangle
Geometry and Trigonometry practice question
A right triangle has sides of length 5, 12 and 13. A similar triangle has a hypotenuse of length 39. What is the perimeter of the similar triangle?
Answer: 90
The scale factor is 39/13 = 3, so every side triples: 15, 36 and 39. Perimeter: 15 + 36 + 39 = 90.
Common wrong answers
- If you answered 30
- 30 is the perimeter of the ORIGINAL triangle (5 + 12 + 13).
- If you answered 56
- 56 is 30 + 26, adding the hypotenuse difference instead of scaling every side.
- If you answered 270
- 270 is 30 × 9, scaling by 3² — that is the ratio for AREAS, not perimeters.
More Geometry and Trigonometry questions
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