Re: Deane Kidd and the Metric System


Craig Sawyers <c.sawyers@...>
 

Memorizing the number .03937 solves the whole problem going either way, to or from inches and
millimeters.
That is a more difficult and much more imprecise number to remember than 25.4. That is by definition
the precise conversion. Whereas 1/25.4 ~ 0.03937 are the first digits of a repeating decimal (since
it can be expressed as 10/254, and a fraction of two integers always returns a repeating decimal, as
a simple example 1/9 = 0.11111...). It turns out that the repeat length of 1/254 (and hence of
10/254 = 1/25.4)) is 42 digits long!

Craig

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