A hemispherical brass bowl has inner- diameter 10.5 cm. Find the cost of tin-plating it on the inside at the rate of Rs 16 per 100 cm2.
A hemispherical brass bowl has inner- diameter 10.5 cm. Find the cost of tin-plating it on the inside at the rate of Rs 16 per 100 cm2.

Solution:

Given inner diameter of the brass bowl, d = 10.5 cm

Radius, r = d/2 = 10.5/2 = 5.25 cm

Curved surface area of the bowl = 2r2

= 2×(22/7)×5.252

= 173.25 cm2

Rate of tin plating = Rs.16 per 100 cm2

So total cost = 173.25×16/100 = 27.72

Hence the cost of tin plating the bowl on the inside is Rs. 27.72.