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how to find cubic feet of a cylinder?

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  • how to find cubic feet of a cylinder?

    I need to know how many cubic feet are in a hole that is 2" in Diameter and 9' deep.

    Can you help?

  • #2
    Re: how to find cubic feet of a cylinder?

    Originally posted by chuuxx
    I need to know how many cubic feet are in a hole that is 2" in Diameter and 9' deep.

    Can you help?
    Well, you need the diameter in feet 2"/12"/ft = 1/6 ft or 0.1667 ft.

    Volume of cylinder is
    V = (pi/4)*d*d*h so (3.14159/4)*(1/6)*(1/6)* 9 = 0.1963 ft

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    • #3
      Re: how to find cubic feet of a cylinder?

      Is that 3.14 divided by 4?

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      • #4
        Re: how to find cubic feet of a cylinder?

        Originally posted by chuuxx
        Is that 3.14 divided by 4?
        Yes, althouh "pi" has an infinite number of digits. Some use 3.14, some use 3.14159; usually the rest of the numbers aren't exact enough to use too many digits. I actually used the "pi" key on my calculator.

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        • #5
          Re: how to find cubic feet of a cylinder?

          I come up with .1964280 cubic feet......that don't seem right.

          To find the volume of a cylinder; I thought it was 3.14 x radius squared x 9
          3.14 x .006947 x 9
          is that not correct?

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          • #6
            Re: how to find cubic feet of a cylinder?

            Originally posted by chuuxx
            I come up with .1964280 cubic feet......that don't seem right.

            To find the volume of a cylinder; I thought it was 3.14 x radius squared x 9
            3.14 x .006947 x 9
            is that not correct?
            You can use either (pi)*r*h or (pi/4)*d*h
            The divide by 4 is equivalent to getting radius (squared) from diameter. Same thing.

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            • #7
              Re: how to find cubic feet of a cylinder?

              May I ask what answer you may have gotten? I am correct....lol?

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              • #8
                Re: how to find cubic feet of a cylinder?

                I gave the answer in post #2 (at end). We agree within rounding of pi and the fractional foot radius or diameter.

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                • #9
                  Re: how to find cubic feet of a cylinder?

                  thanks for your help!

                  Comment


                  • #10
                    Re: how to find cubic feet of a cylinder?

                    I have to figure how many bags of grout to fill a hole.
                    The hole is 75' deep and 4" in diameter.
                    The bags are 1.29 cubic feet each

                    Thank you for your help!

                    Comment


                    • #11
                      Re: how to find cubic feet of a cylinder?

                      Originally posted by ghco View Post
                      I have to figure how many bags of grout to fill a hole.
                      The hole is 75' deep and 4" in diameter.
                      The bags are 1.29 cubic feet each

                      Thank you for your help!
                      5.1 bags. See post #2 for method and convert 4" to 0.333... ft

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                      • #12
                        Re: how to find cubic feet of a cylinder?

                        Thanks John,

                        I'm still doing something wrong and not sure what...I've followed your info on Post 2 and still messing something up....I have to take a test and WANT to know how to do this..even in the field for calcualtions on amount of supplies to order!
                        Never said I was smart...hahahaha!
                        Thanks again!

                        Comment


                        • #13
                          Re: how to find cubic feet of a cylinder?

                          Originally posted by Unregistered View Post
                          Thanks John,

                          I'm still doing something wrong and not sure what...I've followed your info on Post 2 and still messing something up....I have to take a test and WANT to know how to do this..even in the field for calcualtions on amount of supplies to order!
                          Never said I was smart...hahahaha!
                          Thanks again!
                          Hi There, what are the dimensions you have? - Remember to use the same units for the diameter and the height, for example feet.

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                          • #14
                            Re: how to find cubic feet of a cylinder?

                            Originally posted by Unregistered View Post
                            Thanks John,

                            I'm still doing something wrong and not sure what...I've followed your info on Post 2 and still messing something up....I have to take a test and WANT to know how to do this..even in the field for calcualtions on amount of supplies to order!
                            Never said I was smart...hahahaha!
                            Thanks again!
                            I don't believe you're calculating the size of the grout bags.

                            Once the volume of the hole in ft3 is calculated, you have to divide it by the volume contained in each bag in ft3

                            4"/12" = 0.333 ft

                            (PI/4) * 0.333 ft * 0.333 ft * 75 ft = 6.53 ft3 hole volume
                            6.53 ft3 / 1.29 ft3/bag = 5.06, rounded up to 5.1 bags

                            Comment


                            • #15
                              Re: how to find cubic feet of a cylinder?

                              Thank you very much Mrs X & Dirtman!
                              I got it now and certainly not without your help!
                              Thank you again JohnS.

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