#### Question

In a sphere the rate of change of surface area is

##### Options

8π times the rate of change of diameter

2π times the rate of change of diameter

2π times the rate of change of radius

8π times the rate of change of radius

#### Solution

8π times the rate of change of radius

\[\text { Let r be the radius and S be the surface area of the sphere at any time t .Then },\]

\[S = 4\pi r^2 \]

\[ \Rightarrow \frac{dS}{dt} = 8\pi r\frac{dr}{dt}\]

\[ \therefore \text { The rate of change of surface area is } 8\pi \text { times the rate of change of the radius.}\]

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In a Sphere the Rate of Change of Surface Area is (A) 8π Times the Rate of Change of Diameter (B) 2π Times the Rate of Change of Diameter (C) 2π Times the Rate of Change of Radius Concept: Rate of Change of Bodies Or Quantities.

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