A closed iron tank 12m long,9m wide and 4m deep is to be made .determine the cost of iron sheet used at the rate of rupees 50 per metre the sheet being 2m wide.

length = 12m  ;  breadth = 9m ;  height = 4m

TSA of the tank = 2[length×breadth + breadth×height + height×length] = 2[12×9+9×4+4×12]

 = 384 m²

Area of the rectangular iron sheet = 384 m²

so, length × breadth = 384 ⇒ length = 384 / 2 = 192 m  [as sheet is 2 m wide]

Now total cost of the sheet = Rs. (192 × 50) = Rs. 9600