The radius of a spherical balloon increases from 7 {\cm} to 14 {\cm} as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases

Sainik School Entrance Exam 2019 Solved Paper

Question : 44 of 150

Marks: +1, -0

The radius of a spherical balloon increases from

7 {\cm}

14 {\cm}

as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases

Solution:

(a) We know, surface area of sphere

=4 πr^2

Hence, required ratio

={4≠r_1^2}/{4 ≠r_2^2}

=({r_1}/{r_2})^2=({7}/{14})^2=1: 4.

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