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 50 per metre . the sheet is 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]
=2[108+36+48]

 = 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