A hollow semi-circular vessel whose diameter inside and outside is 43 and 42 cm respectively and if the cost of painting it is 7 paise per square centimeter, then what is the cost of getting it painted?
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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 =2πr12+2πr22+π(r2−r1)2
where r2=43cm and r1=42cm
∴ area = π(2×422+2×432+12)
=22,704.290 cm2
∴cost=7×22,704.290=158,930.46 paisa
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