Using Heron's formula, what is the area of a triangle with side lengths 7 cm, 8 cm, and 9 cm?
Answer and explanation
Correct answer: C. 12 sqrt(5) cm^2
- Step 1: Semi-perimeter s = (7 + 8 + 9)/2 = 12 cm. Step 2. Area = sqrt(12 (12 - 7) (12 - 8) (12 - 9)) = sqrt(12 5 4 3) = sqrt(720) = sqrt(144 5) = 12 sqrt(5) cm^2. Answer: 12 sqrt(5) cm^2. Why not the others:* 24 sqrt(5) forgets square root on 144.
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