Calculus

The function V=4pir^2 describes the volume of a right circular cylinder of heigh 4ft and radius r feet. Find the (instantaneous) rate of change of the volume with respect to the radius when r=6. Leave the answer in terms of pi.

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  1. dV/dr = 8pir*dr/dr
    which at r = 6 is 8pi(6)
    =48pi

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  2. actually the answer is 64pi ft^3/ft.
    can you figure out what you did wrong? thanks.

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  3. Nope, for the data you gave me the answer is 48pi

    this is a very straighforward question,
    to have an answer of 64 pi, perhaps you were to find the rate when r = 8.
    Check your typing

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  4. sorry. yes, r should be equal to 8. Thanks.

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