Q. 243.8( 13 Votes )

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 = 10.5cm

External radius, R = 12.6cm

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 cm2 of surface = 10paise

Therefore, total cost to paint 1843.38 cm2 =

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