The internal and external diameters of a hollow hemispherical vessel a

1.	The internal and external diameters of a hollow hemispherical vessel are 21 cm and 25.2 cm respectively. The cost of painting 1 cm2 of the surface is 10 paise. Find the total cost to paint the vessel all over.
Answer» Given that, internal diameter of hollow hemisphere, r = 10.5 cm External radius, R = 12.6 cm Total surface area = 2πR² + 2πr² + π(R² - r²) = 2π(12.6)² + 2π(10.5)² + π((12.6)² – (10.5)²) = 1843.38 cm² Given that, cost of painting 1 cm²of surface = 10 paise Therefore, total cost to paint 1843.38 cm² = \(\frac{1843.38\times10}{100}\) Rs 184.34

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

Answer»

Given that,

internal diameter of hollow hemisphere, r = 10.5 cm

External radius, R = 12.6 cm

Total surface area = 2πR² + 2πr² + π(R² - r²)

= 2π(12.6)² + 2π(10.5)² + π((12.6)² – (10.5)²)

= 1843.38 cm²

Given that,

cost of painting 1 cm²of surface = 10 paise

Therefore, total cost to paint 1843.38 cm² = \(\frac{1843.38\times10}{100}\)

Rs 184.34