Question

A plastic box 1.5 m long, 1.25 m wide and 65 cm deep is to be made. It is opened at the
top. Ignoring the thickness of the plastic sheet, determine:
The area of the sheet required for making the box.
The cost of sheet for it, if a sheet measuring Im costs Rs 20.
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Answer 1

Answer:

Here, l = 1.5 m, b = 1.25 m, h = 65 cm = 0.65 m. Since the box is open at the top, it has only five faces. (i) So, surface area of the box = lb + 2(bh + hl) = 1.5 × 1.25 m2 + 2 (1.25 × 0.65 + 0.65 × 1.5) m2 = 1.875 + 2 (1.7875) m2 = (1.875 + 3.575) m2 = 5.45 m2 Hence, 5.45 m2 of sheet is required Ans. (ii) Cost of 1 m2 of the sheet = Rs 20 ∴ cost of 5.45 m2 of the sheet = Rs 20 × 5.45 m2 = Rs 109