A triangular plot has sides 17 m, 25 m and 28 m. What is its area?

210 m²Correct answerYour answer212.5 m²Correct answerYour answer238 m²Correct answerYour answer350 m²Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer A

Correct answer: A

Use Heron's formula. Semi-perimeter $s = (17 + 25 + 28) \div 2 = 35$ m.
Area = $\sqrt{35 \times 18 \times 10 \times 7} = \sqrt{44{,}100} = 210$ m².

Worth noting

The plot is not right-angled $(17^2 + 25^2 \ne 28^2)$ , so ½ × one side × another is wrong: that gives 212.5, 238 or 350 m², depending on which two sides are used.

Concept: Heron's formula for a scalene triangle
Typical timeTypical: 70 s
Your timeYours: —

The rule this testsPerimeter and area

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A triangular plot has sides 17 m, 25 m and 28 m. What is its area?

Explanation