Difficulty: Medium
Correct Answer: 5√63 sq cm
Explanation:
Introduction / Context:Heron’s formula computes the area of any triangle from its three side lengths, avoiding angle or height calculations. The key steps are finding the semiperimeter and then evaluating the square root expression carefully to keep radicals simplified.
Given Data / Assumptions:
Concept / Approach:Heron’s formula: Area = √[s(s − a)(s − b)(s − c)]. Compute s, the three differences, and multiply; then take the square root. Simplify the radical by extracting perfect squares to match common answer forms.
Step-by-Step Solution:
s = (8 + 10 + 12)/2 = 15.Compute factors: s − a = 7, s − b = 5, s − c = 3.Product: s(s − a)(s − b)(s − c) = 15 * 7 * 5 * 3 = 1575.Simplify: 1575 = 9 * 175 = 9 * 25 * 7 ⇒ √1575 = √(9*25*7) = 3*5*√7 = 15√7.Note that 15√7 = 5√(9*7) = 5√63, matching the given option form.Verification / Alternative check:
Approximate value: √7 ≈ 2.6458 ⇒ area ≈ 15 * 2.6458 ≈ 39.69 sq cm.Why Other Options Are Wrong:
Common Pitfalls:
Final Answer:5√63 sq cm (which equals 15√7 sq cm).
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