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.
Given,
Length of closed iron tank = 12m
Breadth = 9m
Height = 4m
Total surface area of tank = 2(12×9+9×4+4×12) = 2(192) = 384 m2
Width of iron sheet = 2m (given)
So, length of iron sheet = 
Hence, cost of iron sheet at rate Rs.5 per meter = 5×192 = Rs.960
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