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

It is given that, length (l) of box = 1.5 m
Breadth (b) of box = 1.25 m
Depth (h) of box = 0.65 m
(i) Box is to be open at top.
Area of sheet required
= 2lh + 2bh + lb
= [2 × 1.5 × 0.65 + 2 × 1.25 × 0.65 + 1.5 × 1.25] m2
= (1.95 + 1.625 + 1.875) m2 = 5.45 m2
(ii) Cost of sheet per m2 area = Rs 20
Cost of sheet of 5.45 m2 area = Rs (5.45 × 20)
= Rs 109
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