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Homework Help: Find the volume of a frustum of a right circular cone

  1. Feb 1, 2009 #1
    Find the volume of a frustum of a right circular cone with height h, lower base radius R, and top radius r.

    I don't want the answer. I want to know how to do this. My math teacher gave all of these problems for the class to do, but didn't explain anything. Are there equations that I can use and what do I need to do to find the volume?
  2. jcsd
  3. Feb 1, 2009 #2


    Staff: Mentor

    Re: Volumes

    Imagine that the cone frustum is sliced into horizontal circular slices. What is the volume of one of these slices? Add all the slices (i.e., integrate) to get the total volume.

    To get the volume of a slice, you need its radius, which varies from R at the bottom to r at the top.

    You should make a graph of the cross section of the cone frustum. What you really need it the equation of the line that runs from (R, 0) to (r, h). Calculate the slope and use either point to get the equation. The x values on this line represent radii of your circular slices.
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