Decimal arithmatic, was Re: Python GUI app to impress the boss?

James J. Besemer jb at
Wed Oct 2 09:38:40 CEST 2002

Dennis Lee Bieber wrote:

>        When I took science classes, I'd have been dinged a few points if I 
>turned in 0.035 -- the rule was to report results to the same 
>significance as the inputs.
>        0.7 * 0.05 => 0.0 in those science classes. The assumption here being 
>that the accuracy of measurements is such that the last supplied 
>decimal place is already an estimate -- one does not add places which 
>imply increased precision.

Wow.  That's pretty Wierd Science, if you ask me.  ;o)

You must have gotten a lot of ZEROS whenever using universal constants, 
like Planck's Constant, Avogadro's number, Amperes, Joules, Ergs or 
Electron Volts vs. any practical quantity in chemistry or physics class. 

I think you're confusing some other message about precision.  E.g., I 
suspect you were supposed to learn that

    0.7 * 0.05 => 0.04     ( instead of 0.035)

Precision -- the number of significant digits is independent of the 
scale factor, or magnitude, of the number.



James J. Besemer		503-280-0838 voice
2727 NE Skidmore St.		503-280-0375 fax
Portland, Oregon 97211-6557	mailto:jb at	

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