Length of the open box, l = 1.5 m
Breadth of the open box, b = 1 m
Height of the open box, h = 1 m
Surface area of open box = Total surface area of the box − Area of the top
=2(l×b+b×h+h×l)−l×b
=2(1.5×1+1×1+1×1.5)−1.5×1
=2(1.5+1+1.5)−1.5
=2×4−1.5
=8−1.5
=6.5 m2
Hence, 6.5 m2 of the sheet will be needed to make the open box.
Now, it is given that the inside and the outside surface of the open box is to be painted with rust proof paint.
∴ Total area of the box to be painted =2× Surface area of open box
=2×6.5
=13 m2
Now, cost of painting of 1 m2 of area = 150 rupees
∴ Cost of painting of 13 m2 of area = 16 × 150 = 1950 rupees
Hence, it will cost 1950 rupees to paint the open box from inside and outside with rust proof paint.