A plastic box 1.5m long, 1.25m wide and 65cm deep is to be made. It is opened at the top. Ignoring the thickness of the plastic sheet, (i) determine the area of the sheet (ii) the cost of sheet for it, if a sheet measuring 1m² costs Rs.20.

Given:Length of box=1.5m, Breadth=1.25m, Height=0.65m
⇒Area to be white-washed=Area of cuboid−Area of base
(i) Area of sheet required=2lb+2bh+2lh−lb
(i) Area of sheet required=2lh+2bh+lb. [Box is open]=[2×1.5×0.65+2×1.25×0.65+1.5×1.25]m²=(1.95+1.625+1.875)m²=5.45m²
ii) Cost of sheet per m² area=Rs.20
Cost of sheet of 5.45m² area=Rs.5.45×20=Rs.109