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Homework Help: Related rates, conic tank

  1. Mar 8, 2010 #1
    1. The problem statement, all variables and given/known data
    Water si emptying out of a tank at a rate of 4 cubic metres/min. The tank is shaped like an inverted circular cone with a diameter of 8 m at the top. The sides of the cone make a 30 degree with the vertical. Determine the exact value of the rate of change of the water level when the height of the water is 3/4 the height of the cone.


    2. Relevant equations
    v=(1/3) (pi) (r^2) (h)


    3. The attempt at a solution
    v = (1/3) (pi) (3/4(h))^2 (h)
    =(3/16)(pi)(h^3)
    v'=(9/16)(pi)(h^2)(h')

    i don't know where to go from here, as i could use trig to get the height of the tank, but i don't have the height at the time specified. help?
     
  2. jcsd
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