A solid brass sphere of radius 2 1 dm is converted into a right circular cylindrical rod of length 7...........

Quantitative Aptitude (CGL) Mensuration 3D

A solid brass sphere of radius 2.1 dm is converted into a right circular cylindrical rod of length 7cm. The ratio of total surface areas of the rod to the sphere is

3:1

1:3

7:3

3:7

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Explanation:

r=2.1dm
=21cm 1dm=10cm
(4/3)πR^3=πr^2h
(4/3)π×21×21×21=πR^2×7
R^2=21×21×4
R=42cm
total surface area of rod/total surface area of sphere
=2πr(R+r)4πr^2=42(42+7)2×21×21
=49/21=7/3=7:3