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Homework Help: Cost of painting a vessel

  1. May 18, 2008 #1
    1. The problem statement, all variables and given/known data

    The inner and outer radii of a hollow steel hemispherical vessel are 2 cm and 3 cm respectively.what is the total cost of painting the vessel all over at the rate of 70 cents per cm² ?

    [ b]2. Relevant equations[/b]
    Curved surface area of hemisphere=2[pi]*[radius]²

    3. The attempt at a solution
    total Surface area= 2[pi]*{[inner radius]² + [outer radius]²}
    TOTAL cost = 0.7*total Surface area

    is it right?
  2. jcsd
  3. May 18, 2008 #2
    Yes, but you can't forget about the rim, with area PI ( [outer radius]^2 - [inner radius]^2 )
  4. May 19, 2008 #3
    u got a point.i was just falling short of the answer by an iota. Thanks buddy.
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