Question

18. If the radius of a sphere is doubled, then what is the ratio of their surface area?
(a) 1:2
(6) 2:1
(d) 4:1
(c) 1:4
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Answer 1

Step-by-step explanation:

The surface area of a sphere = S 1 = 4 π r^2

Increased surface area of a sphere = S 2 = 4π(2r) ^2

Therefore, S 2 / S 1

$= \frac{4\pi( {2r)}^{2} }{4\pi {r}^{2} }$

$= \frac{4 {r}^{2} }{ {r}^{2} }$

$= \frac{4}{1}$

= 4 : 1

Answer :- The ratio of their surface area is 4 : 1.