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in Mensuration by (35.6k points)
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The radii of two spheres are in the ratio 2 : 3, then the ratio of their surface areas is ………

A) 3 : 2 

B) 27 : 8 

C) 8 : 27 

D) 4 : 9

2 Answers

+1 vote
by (66.4k points)
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Best answer

Correct option is: D) 4 : 9

Given that \(\frac {r_1}{r_2}\) = \(\frac 23\)

\(\therefore\) \(\frac {S_1}{S_2} = \frac {4 \pi r_1^2}{4 \pi r_2^2}\) = \((\frac {r_1}{r_2})^2 = (\frac 23)^2 = \frac 49 = 4 : 9\)

Hence, the ratio of their surface areas is 4 :9.

+1 vote
by (34.5k points)

Correct option is: D) 4 : 9

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