if the height of the roller is 20 cm and its radius is 10 cm then
find its total surface area when:
it has base but no top
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Answer:
Sol: (i) Here, l = 1.5 m, b = 1.25 m
∵ It is open from the top.
∵ Its surface area = [Lateral surface area] + [Base area]
= [2(l + b)h] + [l × b]
= [2(1.50 + 1.25)0.65 m2] + [1.50 × 1.25 m2]
= [2 × 2.75 × 0.65 m2] + [1.875 m2]
= 3.575 m2 + 1.875 m2 = 5.45 m2
∵ The total surface area of the box = 5.45 m2
∴ Area of the sheet required for making the box = 5.45 m2
(ii) Rate of sheet = Rs. 20 per m2
Cost of 5.45 m2 = Rs. 20 × 5.45
⇒ Cost of the required sheet = Rs.109
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