A tank measures 25 m × 12 m × 6 m. If its walls and bottom are plastered at 75 paise per m², what is the total cost?

Problem restatement
Find the interior surface area of the tank (bottom + four walls) and multiply by the rate to get cost.

Given data

• Length = 25 m, width = 12 m, depth = 6 m.
• Rate = 75 paise per m² = Rs. 0.75 per m².

Concept/Approach
Interior area to plaster = bottom area (L × W) + wall areas (2Lh + 2Wh).

Step-by-Step calculation
Bottom = 25 × 12 = 300 m²Walls = 2(25 × 6) + 2(12 × 6) = 300 + 144 = 444 m²Total area = 300 + 444 = 744 m²Cost = 744 × 0.75 = Rs. 558

Verification/Alternative
Unit check: m² × Rs./m² ⇒ Rs.; arithmetic 744 × 3/4 = 186 × 3 = 558.

Common pitfalls
Including the open top or double-counting a wall; the problem specifies walls and bottom only.

Final Answer
Rs. 558