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Volume of cylinders

  1. Sep 15, 2011 #1
    which is greater or are they equal: one cylinder with 2 radius and height 10, or one with 1 radius and height 20

    I thought they would be equal because the first one is

    4pi * 10 = 40pi

    and the second is

    2pi * 20 = 40pi

    But my book says the first is greater. don't understand why
     
  2. jcsd
  3. Sep 15, 2011 #2

    pwsnafu

    User Avatar
    Science Advisor

    Start again. What's the formula for volume of a cylinder?
     
  4. Sep 15, 2011 #3
    ok, pir^2h not pi(2r)h

    now i get it
     
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