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a rectangular room is 20 ft by 12 ft by 8 ft. If the length is decreasing by 4 inches per minute, the width is decreasing by 5 inches per minute and the height remains constant, how fast is the volume changing after 2 minutes?

  • calculus -

    let the width be x
    let the length be y
    let the height be h

    V= xyh
    dV/dt = xy dh/dt + xh dy/dt + yh dx/dt

    given x=20, y=12, h = 8
    dx/dt = 5
    dy/dt = -4
    dh/dt = 0

    Plug in those values into dV/dt

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