Q.1. A piastic 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 m cost Rs 20. Sol. Here, length - 1.5 m, Breadth- 1.25 m, Height - 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 - Ib + 2(bh + hl) 1.5 x 1.25 m? + 2 (1.25 x 0.65 + 0.65 x 1.5) m^2 = 1.875 + 2 (1.7875) m^2 = (1.875 + 3.575) m2 - 5.45 m^2 Hence, 5.45 m^2of sheet is required Ans. (ii) Cost of 1 m^2of the sheet = Rs 20 . cost of 5.15 m^2 of the sheet = Rs 20 x 5.15 m^2 = Rs 109 Ans. Q.2. The length, hreadth and height of a room are 5 m,3 m and 3m. respectively. Find the cost of white washing the walls of the room and the ceiling at the rate of Rs 37.50 per m^2. Sol. Here, l = 5 m, b = 4 m, h = 3 m Surface area of the walls of the room and the c...
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