Question

1.
EXERCISE 13.1
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:
(i) The area of the sheet required for making the box.
(ii) The cost of sheet for it, if a sheet measuring 1m² costs * 20.
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Answer 1

Answer:

I) Here, length (l) = 1.5 m, bread th(b) = 1 .25 m

and height (h) = 65 cm = 65100 m = 0.65 m

∵ It is open from the top.

∴ Its surface area

= [Lateral surface area] + [Base area]

= [2(1 + b)h] + [lb]

= [2(1.50 + 1.25)0.65] m2 + [1.50 x 1.25] m2

= [2 x 2.75 x 0.65] m2 + [1.875] m2

= 3.575 m2+ 1.875 m2 = 5.45 m2

∴ Area of the sheet required for making the box = 5.45 m2

(ii) Cost of 1 m2 sheet = Rs. 20

Cost of 5.45 m2 sheet = Rs. (20 x 5.45)

= Rs. 109

Hence, cost of the required sheet = Rs. 109

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