Read the following passage and answer the questions given at the end:

Students of Class XII presented a gift to their school in the form of an electric lamp in the shape of a glass hemispherical base

Question

Read the following passage and answer the questions given at the end:

Students of Class XII presented a gift to their school in the form of an electric lamp in the shape of a glass hemispherical base surmounted by a metallic cylindrical top of same radius 21 cm and height 3.5 cm. The top was silver coated and the glass surface was painted red.

(i) What is the cost of silver coating the top at the rate of ₹5 per 100 cm$^2$?
(ii) What is the surface area of glass to be painted red?

Accepted Answer

Step 1: (i) Surface Area of the top $= 2 	imes \frac{22}{7} 	imes 21 	imes 3.5 = 462$ cm$^2$. Cost of silver coating $= 462 	imes \frac{5}{100} = $ ₹$23.10$
Step 2: (ii) Surface Area of glass $= 2 	imes \frac{22}{7} 	imes 21 	imes 21 = 2772$ cm$^2$

Question

Solution