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Related Rates cylinder problem

  1. Feb 11, 2008 #1
    A cylinder is placed in oven where both the height and base radius expand at 0.1 mm/min. When the height is 250 mm and the radius of the base 30 mm, the volume is expanding at ......mm3 /min. (Answer to nearest whole number)

    r=30, h=250, dr/dh=0.1, dh/dt=0.1

    dV/dt = (pi)r^2(dh/dt) + 2rh(dr/dt)
    =(pi(30)^2(0.1) + 2(30)(250)(0.1)
    =1783

    Can anybody please show me where I'm going wrong with this one?
     
  2. jcsd
  3. Feb 11, 2008 #2
    [tex]V=\pi r^2h[/tex]

    You're missing a pi term!

    [tex]\frac{dV}{dt}=\pi[2hr\frac{dr}{dt}+r^2\frac{dh}{dt}][/tex]
     
  4. Feb 12, 2008 #3
    Thanks roco!
     
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