L/100 km is a more user-friendly measurement, especially if one is concerned about $/L (or in my case £/L) but an area has a specific meaning: a fuel consumption of 0.1 mm^2 means that conceptually your vehicle takes in fuel as it is travelling from a stationery pipe lying on the road that has a cross-section of 0.1 mm^2.
From: John M. Steele [mailto:[email protected]] Sent: 16 March 2015 10:33 To: [email protected]; U.S. Metric Association Subject: Re: [USMA:54641] Re: Adoption of the metric system in medicine Most lab (blood) tests in the US use a denominator of deciliter and whatever prefix is convenient in the numerator. I think the reason is that 1 g/dL = 1% on a weight/volume basis. I suspect that is a carryover of some prior practice even though most "interesting" results are a fraction of a percent. I have nothing that "proves" that, just an observation and suspicion. Yes, fuel consumption reduces to an area if you "simplify" units. I support doing that in cases where it adds clarity. I think you would have to admit that, in this case, it "subtracts clarity." _____ From: Martin Vlietstra < <mailto:[email protected]> ^2. > To: U.S. Metric Association <[email protected]> Sent: Monday, March 16, 2015 3:19 AM Subject: [USMA:54641] Re: Adoption of the metric system in medicine It appears to me that certain parts of the medical profession use "odd" prefixes so as to avoid using decimal points. For example, in many countries, the sugar level in one's blood is measured in mg/dL. The result should lie between 70 and 120. Values of both 20 and 200 are possible, representing opposite extremes, so blood sugar level, when written in mg/dL should never have a decimal point - ie one should write "20", not "20.0" as the latter could be confused with "200". Another strange use of prefixes is motor car fuel consumption, usually written in L/100 km. If this is reduced to base units, one ends up with a value of the order of 0.1 mm^2! -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of James Sent: 16 March 2015 00:56 To: U.S. Metric Association Subject: [USMA:54640] Re: Adoption of the metric system in medicine Avoiding the use of prefixes for units in the denominator is fairly common as a "style" (as opposed to a requirement) but that's not a rigid guideline. As we've discussed, there are many reasons one might use prefixed units in a denominator which "override" that style. My view of the SI is that it is designed to be as flexible as possible. The limited number of "requirements" exist only to prevent ambiguities and to provide formatting consistent with its underlying quantity calculus. A common fault of some new adherents to the SI, in my opinion, is to impose rigidity that was not written in to the standard, namely the SI Brochure. That has led, on this list, to what I consider silly arguments, such as the pronunciation of kilometer and derogation of the four "small" prefixes between kilo and milli. I think that we should keep in mind that the SI's primary purpose is to facilitate commerce (Treaty of the Meter) and that is done by clearly, simply, reliably, and unambiguously presenting the values of quantities. Science provides the technical realizations to cover "reliably" and the quantity calculus covers the rest of those attributes. That's a gross generalization but it makes a pretty picture in my mind. Jim On 2015-03-15 18:52, Pierre Abbat wrote: > On Wednesday, February 11, 2015 20:31:08 James wrote: >> Strangely, Chapter 5 of the SI Brochure is silent on that, Pierre. At >> least, I could find nothing on the matter. When you describe this >> "proper" style, which standard are you using for your reference? Would >> you please provide a quote of its statement to that effect and it's >> clause or section number? > > I don't remember the reference; it was something I picked up when studying for > the CMS test. One doesn't put milliseconds or kiloseconds in the denominator, > but one does put kilograms, because the kilogram is a base unit. > > Pierre > -- James R. Frysinger 632 Stoney Point Mountain Road Doyle TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108
