A tank open at the top is made of iron sheet 4 m wide. If the dimensions of the tank are 12m×8m×6m, find the cost of iron sheet at Rs. 17.50 per metre.
Given,
Dimensions of tank = 12m × 8m × 6m
Where length = 12m , breadth = 8m , height = 6m
Area of sheet required for making the tank = total surface area of tank with one top open
= 
Let 
= 
= 
= 
So,
Cost of iron sheet at rate Rs.17.50 per metre = 17.50 ×84 = Rs.1470
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