Plastering a rectangular tank (inside walls + bottom): A tank is 25 m long, 12 m wide, 6 m deep. Find cost of plastering its walls and bottom at Rs 0.75 per sq. m.
Aptitude
Area
Difficulty: Easy
Choose an option
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ARs. 258
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BRs. 358
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CRs. 458
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DRs. 558
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ENone of these
Answer
Correct Answer: Rs. 558
Explanation
Introduction / Context:Compute interior area to be plastered (four walls + bottom) and multiply by the given rate.
Given Data / Assumptions:
- Length L = 25 m, width W = 12 m, depth H = 6 m.
- Rate = Rs 0.75 per m^2.
Concept / Approach:Area to plaster = bottom + all four interior walls.
Step-by-Step Solution:
Bottom area = L*W = 25*12 = 300 m^2.Long walls = 2*(L*H) = 2*(25*6) = 300 m^2.Short walls = 2*(W*H) = 2*(12*6) = 144 m^2.Total = 300 + 300 + 144 = 744 m^2.Cost = 744 * 0.75 = Rs 558.Verification / Alternative check:Unit-check: m^2 * Rs/m^2 ⇒ Rs — consistent.
Why Other Options Are Wrong:Other totals correspond to incorrect wall counts or missing the bottom.
Common Pitfalls:Including the top (open tank), or double-counting a pair of walls.
Final Answer:Rs. 558