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### Gallons and Cubic Inches

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Date: 09/04/2001 at 11:13:26
From: Darryl Nester
Subject: Volume conversion - history

I know that 1 gallon is 231 cubic inches, based on the old English
"wine gallon" unit. But I have not been able to find out WHY the
number 231 was used. Was it simply the case that at some point in the
process of standardizing volume measurements, it was determined that a
wine gallon was "pretty close to" 231 cubic inches, so someone decided
to use that number from then on? Or was there some deeper reason for
this choice?
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Date: 09/04/2001 at 16:49:29
From: Doctor Rick
Subject: Re: Volume conversion - history

Hi, Darryl.

You can find some information on this page (under "Volume"), from the
"How Many?" site by Russ Rowlett,  linked from our Dr. Math FAQ:

http://www.unc.edu/~rowlett/units/custom.html

It doesn't say exactly how the wine gallon was defined. The following
page indicates the original definition of the wine gallon:

Weights & Measures 1: An American Encyclopedia
http://www.todd.demon.co.uk/encyc/measures1.htm

I quote:

"In 1824, the British abandoned both the Ale and the Wine gallons
in favour of the Imperial gallon, based on the volume of 10 pounds
of water (which works out at 277.41945 cu in). America, by this
inches (strictly speaking, this was defined as the volume of a
cylinder 6 inches long and 7 inches in diameter, or 230.9070 cubic
inches)."

Indeed, the volume of this cylinder is

V = pi*r^2*h = 3.14159 * (7 inches/2)^2 * (6 inches)
= 230.90706 cubic inches

- Doctor Rick, The Math Forum
http://mathforum.org/dr.math/
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Associated Topics:
High School History/Biography
Middle School History/Biography
Middle School Terms/Units of Measurement

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