A hemispherical vessel has inner and outer Radii as 3 inches and 5 inches respectively. Its total surface has to be polished at the rate of Rs 10 for every π inch^2. Find the total cost of polishing the vessel.
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Step-by-step explanation:
Internal diameter of spherical vessel =42 cm
External diameter of hemispherical vessel =43 cm
Internal radius =r=21 cm and External radius =R=21.5 cm
Total surface area to be painted
= External curved surface + Internal curved surface + Area of ring
Curved surface area of hollow hemisphere =2πr
1
2
+2πr
2
2
+π(r
2
−r
1
)
2
where r2=43cm and r
1
=42cm
∴ area = π(2×42
2
+2×43
2
+1
2
)
=22,704.290 cm
2
∴cost=7×22,704.290=158,930.46 paisa
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