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Get Answers to all your Questions
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 Rs 5 per 100 cm2 ?
(ii) What is the surface area of glass to be painted red ?
Answers (1)
Radius of cylindrical top ;
Height of cylindrical top ;
The area which has to be coated silver is curved surface area of cylindrical top + upper of cylinder
Curved surface area of cylinder =
So, area to be coated silver = 
=
Cost of coating Rs
Cost of coating
Rs
(using unitary method)
Cost of coating 
Rs
Area of glass to be painted red is curved surface area of hemisphere
Radius of hemisphere ;
Curved Surface area of hemisphere
So, surface area of glass to be painted 
×
×
×
