Difficulty: Medium
Correct Answer: 360 sq metre
Explanation:
Introduction / Context:First recover the rectangle’s dimensions, compute its diagonal, then evaluate the triangle area using base = diagonal and height = length.
Given Data / Assumptions:
Concept / Approach:Solve for L and B, compute diagonal d = √(L^2 + B^2), then triangle area A = (1/2)*d*L.
Step-by-Step Solution:
1) (B + 6) + B = 42 ⇒ 2B = 36 ⇒ B = 18; L = 24.2) d = √(24^2 + 18^2) = √(576 + 324) = √900 = 30 m.3) Triangle area = 0.5 * 30 * 24 = 360 sq m.Verification / Alternative check:Dimensions satisfy perimeter 2(24 + 18) = 84.
Why Other Options Are Wrong:380, 400 do not match the computed area; “360 metre” has wrong units for area.
Common Pitfalls:Using 2(L+B) wrongly or forgetting to halve for triangle area.
Final Answer:360 sq metre.
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