The length of radius of a spherical gas ballon increases from 7 cm to – InterviewSolution

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1.	The length of radius of a spherical gas ballon increases from 7 cm to 21 cm as air is being pumped into it, then find the ratio of surface areas of the ballon in two cases .
Answer» The previous radius of the balloon `=4xx(22)/(7)xx7^(2)` sq.cm `therefore` the ratio of the whole surface areas of the balloon in two cases `=4xx(22)/(7)xx7^(2):4xx(22)/(7)xx21^(2)=(7xx7)/(21xx21)=(1)/(9)=1:9`. Hence the required ratio=1:9.

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