Q. 14.3( 49 Votes )

(a) r = 3 cm (b) r = 4 cm

Answer :

(a) We know that area of a circle (A) is A = πr^{2}

Then, Rate of change of the area with respect to its radius is given by,

When r = 3cm

Then

Therefore, the area of the circle is changing at the rate of 6πcm^{2}/s when its radius is 3cm.

(b) We know that area of a circle (A) is A = πr^{2}

Then, Rate of change of the area with respect to its radius is given by,

When r = 4cm

Then

Therefore, the area of the circle is changing at the rate of 8πcm^{2}/s when its radius is 4cm.

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