A hemispherical dome is open from its base and is made of iron. Thickness of dome is 3.5 meter. Total cost of painting domes outer curved surface is Rs 2464. If the rate of painting is Rs 8 per meter2, then what is the volume (in meter3) of iron used in making dome?
Show answer & explanation
Correct answer: D
Explanation
The correct option is 4.
Total cost of painting domes outer curved surface is Rs 2464.
And the rate of painting is Rs 8 per meter2.
So, Total curved surface area = 
m2 = 308 m2.
So, 2πr2 = 308.
or, r2 = 
= 49.0197.
or, r = 7.0014.
So, Total Volume = 
πr3 = π × 7.00143 = 718.8086 m3.
Volume of inside = π × 3.53 = 89.7971 m3.
So, Volume of iron = (718.80 − 89.7971) m3 ≃ 629 m3.