Geometry and TrigonometryMediumPerimeter of a right triangle from its legs
Geometry and Trigonometry practice question
The legs of a right triangle measure 9 and 12. What is the perimeter of the triangle?
Answer: 36
The hypotenuse is √(81 + 144) = √225 = 15, so the perimeter is 9 + 12 + 15 = 36.
Common wrong answers
- If you answered 15
- 15 is only the hypotenuse; the perimeter adds all three sides.
- If you answered 21
- 21 is the two legs alone; include the hypotenuse 15.
- If you answered 54
- 54 is the AREA doubled (9 · 12 ÷ 2 = 54 is the area); the perimeter is 36.
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