Question

Find the surface area of a copper sheet required to cover a semi spherical tomb of radius 7m
while the mass of 1m' of the sheet is 2kg. Also calculate the cost of the sheet at Rs. 300 per kg.
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Answer 1

answer 109

step by step explanation

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