# Find the Rate of Change of the Area of a Circle with Respect to Its Radius R When R = 4 Cm - Mathematics

Find the rate of change of the area of a circle with respect to its radius r when r = 4 cm

#### Solution

The area of a circle (A)with radius (r) is given by,

A = pir^2

Now, the rate of change of the area with respect to its radius is given by,

(dA)/(dr) = (d)/(dr)(pir^2) = 2pir

When r = 4 cm,

(dA)/(dr) = 2pi (4) = 8pi

Hence, the area of the circle is changing at the rate of 8π cm when its radius is 4 cm.

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#### APPEARS IN

NCERT Class 12 Maths
Chapter 6 Application of Derivatives
Q 1.2 | Page 197

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