The radius of the circle is given to be r = 6.
We know that the area of a circle is given by A = pi r2 (πr2)
Hence, the rate of chenge of area of a circle with respect to radius r is dA/ dr
A = pi r2
So, dA/ dr = 2 pi r
= 2 pi . 6
= 12 pi.
Hence (B) is the correct option.
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Latika Leekha
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