16Hit1600
Geometry and TrigonometryHardScaling a triangle by its longest side

Geometry and Trigonometry practice question

A triangle has sides of length 6, 8 and 10. A similar triangle has a longest side of length 25. What is the length of the similar triangle's shortest side?

Answer: 15

The longest sides correspond: 25/10 = 2.5 is the scale factor. The shortest side scales the same way: 6 × 2.5 = 15.

Common wrong answers

If you answered 20
20 is 8 × 2.5, the MIDDLE side scaled, not the shortest.
If you answered 21
21 is 6 + 15, adding the difference of the longest sides (25 − 10) to the shortest side. Similar figures scale by a ratio.
If you answered 2.4
2.4 scales the wrong way (6 × 10/25); the similar triangle is larger.

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