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Math Help - Put what where?

  1. #1
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    Question Put what where?

    Please help with the formula on how to solve this problem. Sand is being poured onto a conical pile at the rate of 10ft.^3/s. The conical pile's height is always twice its radius. At what rate is the radius of the pile increasing when its height is 4 feet.
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  2. #2
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    Your formula is going to be the Volume of a cone:

    V= 1/3 pi*r^2*h
    since h=2r you have:

    V = 2/3 pi*r^3 ..... You differentiate this with respect to time.

    then you have dV/dt = 10 , and you need to find dr/dt when h=4, same thing as saying r=2.
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  3. #3
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    little more help

    Please set up the rest of the formula.
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  4. #4
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    dV/dt = 2*pi*r^2 * dr/dt

    now plug your values to find dr/dt

    p.s: math is not about getting the problem right but understanding what you are doing.
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