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प्रश्न
A closed iron tank 12 m long, 9 m wide and 4 m deep is to be made. Determine the cost of iron sheet used at the rate of Rs 5 per metre sheet, sheet being 2 m wide.
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उत्तर
\[\text { A closed iron tank of dimensions 12 m long, 9 m wide and 4 m deep is to be made } . \]
\[\text { Surface area of the cuboidal tank = 2 } \times\text { (length }\times \text { breadth + breadth } \times\text { height + length } \times \text { height) }\]
\[ = 2 \times (12 \times 9 + 9 \times 4 + 12 \times 4)\]
\[ = 2 \times (108 + 36 + 48)\]
\[ = 384 m^2 \]
\[\text { Also, the cost of an iron sheet is Rs 5 per metre and the sheet is 2 metres wide } . \]
\[\text { i . e . , area of a sheet = 1 m } \times 2 m = 2 m^2 \]
\[\text { So, the cost of 2 }m^2 \text { of iron sheet = Rs 5 }\]
\[\text { i . e . , the cost of 1 }m^2 \text { of iron sheet = Rs } \frac{5}{2}\]
\[ \therefore \text { Cost of 384 }m^2 \text { of iron sheet = 384 } \times \frac{5}{2} = \text { Rs } 960\]
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