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Homework Help: Find the volume of the pie dish

  1. Dec 7, 2012 #1
    1. The problem statement, all variables and given/known data
    A pie dish is 9 inches across the top, 7 inches across the bottom, and 2.4 inches deep. See the figure above. Compute the volume of this dish. Give your answer correct to 2 decimal places.

    2. Relevant equations

    3. The attempt at a solution

    x=+-3.5, +-4.5

    I'm unsure what to do from here. I'm assuming we are rotating about the y-axis.

    ∫pi(3.5/4.5(y+2.98571))^2-pi(4.5)^2 dy

    I'm not entirely sure what to do. The above expression is obviously wrong, but that's all I could come up with. What exactly am I doing wrong?
  2. jcsd
  3. Dec 8, 2012 #2


    Staff: Mentor

    How did you get this?

    Have you drawn a sketch of the region that will be rotated?

    Assuming that the bottom of the pan is on the x-axis, find the equation of the line between (3.5, 0) and (4.5, 2.4). That line will be the right boundary of the region.
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