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Homework Help: A GRE Question- Cylinder and Volume

  1. Aug 22, 2010 #1
    1. The problem statement, all variables and given/known data
    Jack and Jill each roll a sheet of 9X12 paper to form a cylinder.
    Jack tapes the two 9-inch edges together.
    Jill tapes the two 12-inch edges together.

    Which is greater?
    The volume of Jack's Cylinder
    The volume of Jill's cylinder.

    2. Relevant equations

    Cylinder Volume: V=pi*r^2*h

    3. The attempt at a solution

    The problem that I was facing with this question was finding the radii.
    However, I looked at the solutions and it says that
    Jack's cylinder has a circumference of 12
    and Jill's cylinder has a circumference of 9

    Jack's height is 9
    Jill's height is 12

    I don't understand how they derived the circumferences ?!
    once I know the circumference I can find the radius.

    Last edited: Aug 22, 2010
  2. jcsd
  3. Aug 22, 2010 #2


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    Science Advisor
    Homework Helper

    There's two ways to roll a 9x12 inch piece of paper. If you use the 12 inch side to make the circumference then the 9 inch side must be the height, right? And vice versa? Maybe I don't understand what your question is.
    Last edited: Aug 22, 2010
  4. Aug 22, 2010 #3
    I'm sorry, my question wasn't clear.
    How did they conclude that the circumference is 12 for Jack
    and 9 for Jill
  5. Aug 22, 2010 #4
    ohhh, I see it now :\

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