The internal and external diameters of a hollow hemispherical vessel are 21 cm and 25 2 cm The...........

Quantitative Aptitude ( CCS) Mensuration 3D

The internal and external diameters of a hollow hemispherical vessel are 21 cm and 25.2 cm .The cost of painting 1 cm² of the surface is 10 paisa. Find the total cost to paint the vessel all over.

Rs.184.338

Rs.284.338

Rs.384.338

Rs.484.338

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Explanation:

Given,
Internal diameter of the hollow hemisphere = 21 cm
Internal radius of the hollow hemisphere = 21/2 = 10.5 cm
External diameter of the hollow hemisphere = 25.2 cm
External radius of the hollow hemisphere = 25.2/2 =12.6 cm
Total area of the hollow hemisphere = 2∏R²+2∏r²+∏(R²−r²)
= 2∏12.6²+2∏10.5²+∏(12.6²−10.5²)
= 997.51+692.72 +152.39 cm²
=1843.38 cm²
According to the question,
The cost of painting of 1 cm² of the surface is =10 p =Rs0.01
Then the total cost of painting = 1848.38 * 0.10
=Rs184.338
The total cost of painting all over the vessel is Rs.184.338.