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______?

Answer 1

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.