Question

A dome of a building is in the form of a hemisphere. From inside, it was white-washed at the cost of ₹4989.60. If the cost of white-washing is ₹20 per square meter, find the (i) inside surface area of the dome, (ii) volume of the air inside the dome​

Answer 1

Answer:

Total cost = 498.96 Rs. => Area whitewashed = 249.48 Rs. And according to the question, the area whitewashed is Curved surface area of hemisphere. => 523.908 m³ (approx.)

Answer 2

Step-by-step explanation:

(i) Cost of white-washing the dome from inside = Rs 4989.60

Cost of white-washing 1m2 area = Rs 20

CSA of the inner side of dome = 498.96/2 m2 = 249.48 m2

(ii) Let the inner radius of the hemispherical dome be r.

CSA of inner side of dome = 249.48 m2 (from (i))

Formula to find CSA of a hemi sphere = 2πr2

2πr2 = 249.48

2×(22/7)×r2 = 249.48

r2 = (249.48×7)/(2×22)

r2 = 39.69

r = 6.3

So, radius is 6.3 m

Volume of air inside the dome = Volume of hemispherical dome

Using formula, volume of the hemisphere = 2/3 πr3

= (2/3)×(22/7)×6.3×6.3×6.3

= 523.908

= 523.9(approx.)

Answer: Volume of air inside the dome is 523.9 m3.

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