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How toSolve this related rates question?

Wheat falls from an overhead bin and accumulates in a conical pile, so that the radius of the base of the cone is always twice the height of the cone. If the wheat falls at a rate of 3 m3/min, how fast is the height of the wheat pile changing when the diameter of the pile is 20 meters?

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  • 6 years ago
    Favorite Answer

    Let r = radius, h = height, v = volume, and t = time.

    r = 2h

    v = pir^2 h/3 = pi(2h)^2 h/3 = 4pih^3/3

    d/dt(v) = d/dt(4pih^3/3)

    dv/dt = 4pih^2 (dh/dt)

    When diameter = 10, height = 2.5.

    3 = 4pi(2.5)^2 (dh/dt)

    3 = 25pi dh/dt

    dh/dt = 3/(25pi) = 0.038 m/min

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