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If the ratio of the volume of two spheres is 1:8, then the ratio of their surface area is:
Question

If the ratio of the volume of two spheres is 1:8, then the ratio of their surface area is:

A.

1 : 2

B.

1 : 4

C.

1 : 6

D.

1 : 8

Correct option is B

Given:

Ratio of volumes of two spheres = 1 : 8

Concept Used:

The volume and surface area of a sphere are both functions of the radius.

V ∝ r3 and S ∝ r2

where, V = volume, r = radius, S = surface area

Formula Used:

Volume of a sphere = 43πr3\frac{4}{3}\pi r^3​​

Surface area of a sphere = 4πr24\pi r^2 

Solution:

V1V2=(r1r2)3  r1r2=183=12 Surface Area Ratio=(r1r2)2=(12)2=14\frac{V_1}{V_2} = \left(\frac{r_1}{r_2}\right)^3\\ \ \\ \implies \frac{r_1}{r_2} = \sqrt[3]{\frac{1}{8}} = \frac{1}{2} \\ \ \\\text{Surface Area Ratio} = \left(\frac{r_1}{r_2}\right)^2 = \left(\frac{1}{2}\right)^2 = \frac{1}{4}​​

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