A dome of a building is in the form of a hemi sphere. From inside, it was white-washed at the cost of Rs. 4989.60. If the cost of white-washing isRs20 per square meter, find the (i) inside surface area of the dome (ii) volume of the air inside the dome (Assume π = 22/7)

(i) Given

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

The Cost of white-washing 1m2 area = Rs 20

Therefore, CSA of the inner side of dome = 498.96/2 m2

= 249.48 m2

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

CSA of the inner side of dome = 249.48 m2

We know that CSA of a hemisphere = 2πr2

2πr2 = 249.48

2×(22/7)×r2 = 249.4

r2 = (249.48×7)/(2×22)

r2 = 39.6

r = 6.3

Hence, the radius r = 6.3 m

The volume of air inside the dome = Volume of hemispherical dome

We know that the volume of the hemisphere = 2/3 πr3

= (2/3)×(22/7)×(6.3)3

= 523.908 m3

= 523.9(approx.)

Therefore, the volume of air inside the dome is 523.9 m3.

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