# Math formula needed

Discussion in 'Shop Talk' started by moopups, Feb 22, 2005.

1. ### moopupsIn Remembrance

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Getting old and can't remember the formula to cypher the cubic inches in 3 inch PVC pipe, or how much length does it take to contain 130 cubic inches? Also, how do you convert fluid ounces to cubic inches?

2. ### agmantooagmantooSupporter

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1 U S fluid ounce = 1.805 cubic inch

nomimal 3 inch diameter (ID) = 88.71 cubic inches per foot....this not PVC

3. ### CosmicWell-Known Member

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3 Inch PVC has an ID if 3.068" and a square inch area of 7.393" so it will take 17.58" inches of 3 inch PVC to contain 130 cubic inches.

4. ### 65284Well-Known MemberSupporter

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I too am getting old and forgetful and it has been a long time since I had to do much math but _IF_ PVC ID is 3.068 wouldn't the formula be 3.068 X 3.1416=9.4248 square inch area? 130 cubes -:- 9.4248=13.7933 of 3" PVC pipe?
That 130 cubic inches should hold 72.02 fluid ounces? I may be wrong, usually am.

5. ### mikellWell-Known Member

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6. ### CosmicWell-Known Member

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Nope :no:

Area of a circle is Pi x Radius Squared.

Therefore ID of 3.068" does yield an area of 7.393" and it still takes 17.58" inches of 3 inch PVC to contain 130 cubic inches.

Yup, 130 cubic inches should hold 72 fluid ounces more or less.

7. ### moopupsIn Remembrance

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I have created 3 soap mold rectangle boxes, the size is 13.25 by 3.5 by 1.5 inches. I calculate that to be 69.5 cubic inches each or 208.4 combined. Now as stated above a cubic inch contains 1.8 fluid ounces, so the 3 molds would hold 115 fluid ounces, are my figures correct?

If I round down to 110 fluid ounces, to make up for mis measurements and mold lining would this be correct?

8. ### wy_white_wolfJust howling at the moon

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I come up with 125 instead of 115

9. ### MELOCMaster Of My Domain

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volume of a cylinder= height x pi x radius squared

Vc = h x pi x r^2