16Hit1600
Geometry and TrigonometryEasySpecial right triangles (30-60-90)

Geometry and Trigonometry practice question

In a 30°-60°-90° right triangle, the shorter leg (opposite the 30° angle) has length 6. What is the length of the hypotenuse?

  1. A. 6√2
  2. B. 6√3
  3. C. 12Correct
  4. D. 18

Answer: C. 12

In a 30-60-90 triangle the sides are in ratio 1 : √3 : 2, with the hypotenuse twice the shorter leg. So hypotenuse = 2(6) = 12. Choice B (6√3) is the longer leg, and choice A (6√2) is the 45-45-90 pattern.

Why the other answers are wrong

A. 6√2
6√2 comes from the 45-45-90 ratio 1 : 1 : √2. This is a 30-60-90 triangle, ratio 1 : √3 : 2, so the hypotenuse is 2(6) = 12.
B. 6√3
6√3 is the longer leg (opposite the 60° angle). The hypotenuse is the shorter leg times 2, so 12.
D. 18
You multiplied the shorter leg by 3 instead of by 2 — the 3 in this triangle appears as √3 for the longer leg, while the hypotenuse is 2(6) = 12.

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