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Question
The internal and external diameters of a hollow hemisphere vessel are 21cm and 25.2 cm The cost of painting 1cm2 of the surface is 10paise. Find total cost to paint the vessel all
over______?
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Solution
Given that internal diameter of hollow hemisphere (r) = `21/2`cm = 10.5cm
External diameter(R) = `(25.2)/2`=12.6cm
Total surface area of hollow hemisphere
`=2piR^2+2pir^2+pi(R^2-r^2)`
`=2pi(12.6)^2+2pi(10.5)^2+pi(12.6^2-10.5^2)`
= 997.51 + 692.72 + 152.39
= 1843.38cm2
Given that cost of painting 1cm2 of surface = 10 ps
Total cost for painting 1843.38 cm2
= 1843.38 x 10 ps
= 184.338 Rs.
∴ Total cot to paint vessel all over = 184.338Rs.
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