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CBSE Class 9 Answered

The radius of a spherical balloon increases from 2.8 cm to 3.5 cm as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases
Asked by Topperlearning User | 18 Oct, 2017, 03:13: PM
answered-by-expert Expert Answer

Case I: when radius (r) = 2.8 cm

begin mathsize 12px style Surface space area space left parenthesis straight S subscript 1 right parenthesis space equals space 4 πr squared
equals 4 cross times 22 over 7 cross times 2.8 cross times 2.8
equals 98.56 space cm squared end style

Case II

When radius (R) = 3.5 cm

 

begin mathsize 12px style Surface space area space left parenthesis straight S subscript 2 right parenthesis space equals space 4 πR squared
equals 4 cross times 22 over 7 cross times 3.5 cross times 3.5
equals space 154 space cm squared end style

Therefore, S1: S2 = 16:25

Answered by | 18 Oct, 2017, 05:13: PM

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