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Math Help - Related Rates 2

  1. #1
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    Related Rates 2

    The trunk of a tree is approximately cylindrical in shape and has a diameter of 1 m when height is 15 m. If the radius is increasing at 0.003 m per annum and the height is increasing at 0.4 m per annum, find the rate of increase of the volume of the trunk.

    I got 0.145pi m^3/annum. but the answer in my text isn't the same as mine.

    My work:

    dV/dt=2pi(0.5) (0.003)(15)+pi(0.5)^2(1)(0.4)
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  2. #2
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    Quote Originally Posted by skeske1234 View Post
    The trunk of a tree is approximately cylindrical in shape and has a diameter of 1 m when height is 15 m. If the radius is increasing at 0.003 m per annum and the height is increasing at 0.4 m per annum, find the rate of increase of the volume of the trunk.

    I got 0.145pi m^3/annum. but the answer in my text isn't the same as mine.

    My work:

    dV/dt=2pi(0.5) (0.003)(15)+pi(0.5)^2(1)(0.4)
    I did exactly that calculation and got a completely different answer! Try it again.
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  3. #3
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    I vote for the OP's value. (Though Captain Black's signature bothers me...)
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