# Questions re the metric system

**URL:** <https://boards.straightdope.com/t/questions-re-the-metric-system/817778>\
**Category:** Factual Questions\
**Created:** [July 12, 2018, 1:39pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778 "2018-07-12T13:39:42Z")\
**Posts on this page:** 20\
**Page:** 4

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**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\
**Post date:** [July 12, 2018, 7:11pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/61 "2018-07-12T19:11:07Z")

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> [@Kobal2](#):
>
> And ? 1m = 39.3701 inches = 3.28084 feet. Y’all don’t have an \*\*exact \*\*measure of this specific, arbitrary distance wot my unit system is based on, so yours is pure shite !1!!  
> (I jest, of course, but you get my point, right ?)

Not the base units or divisions, and it is a straw man to even suggest I am debasing the metric system. I said it is the best option for world standards multiple times.

But 1 foot = 0.3048 meters exactly.

As this is GQ, can you please point out where is said the metric system is _pure shite !1!!_? Or can you provide a cite that shows that my descriptions of the limitations (which all systems have) do not exist? I am quite confident I am being factually correct.

I’ll bow out of this thread, as I forgot how passionate people are about this subject and it appears that talking about the historical justifications, and limitations of systems of measure is impractical.

But an accumulating loss in precision is a very real problem, especially when it is unavoidable by a particular system.

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**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\
**Post date:** [July 12, 2018, 7:13pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/62 "2018-07-12T19:13:44Z")

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Partial repeat, OOT in previous post.

> [@senoy](#):
>
> I’ve never thought about the decile thing. How do Celsius countries do it? If asked the temperature, we’ll frequently give the decile. “It’s going to be up in the 90s today.” Or “It’s going to be in the 40s tonight.” What do you Celsius people do? Just refer to the actual projected high or low? If I say it’s going to be in the 70s, that means something to most people. Do you say the low 20s? What if you’re trying to differentiate between the low and the high decile? Does that just not happen? I’m actually interested.

How do you give someone’s approximate age? The same expressions are used in Spanish. Couple of examples from Spain: _Hoy hará… veintitantos_ (today it’s… twentysomething). _¿A cuánto estamos? Pues no sé, pero diría que veintimucho._ (What’s the temp? Dunnow but I’m guessing twentylots.) And “under 36” or “over 36” are of course important, that being more or less body temp (actual body temp will vary by person, time of day and health status). _¿Qué hace ahi fuera? ¡Más de 36 y subiendo!_ (how hot is it out there? Over 36 and climbing!)

One of the signs of a bad translator or adapter (which may actually mean a bad editor) is that they’ve converted temperatures and not used the usual rounding. “He had a high fever, above 38C” in a British edition becomes “he had a high fever, above 100.4F” in the American edition. Because yeah, the decimal is what’s sooooo important.

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**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\
**Post date:** [July 12, 2018, 7:17pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/63 "2018-07-12T19:17:25Z")

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> [@Orwell](#):
>
> I cook a lot, actually. I know I like to cook my steaks to 125 and I like to BBQ at 225 to 250. I bake stuff at 350 most of the time, but sometimes at 300, 325, 400 or 425.
> 
> When I need to boil water, I heat it until I see the bubbles coming to the top. I don’t stick a thermometer in it to see if it is 212 F or 100 C. When I need to freeze something, I stick it in the freezer until it’s solid. No measurement necessary.
> 
> I was referring to teaspoons, tablespoons, etc. I think it would be much easier to use 5ml, 10ml, etc when trying to halve or double a recipe.

Don’t worry boo, metric cookbook writers still use obnoxiously vague “units” like a pinch, a dash, a sprinkle, a spritz, “as needed” (if I knew how much was needed I wouldn’t need to buy a fucking recipe, now would I ?!), a cup (FUCK YOU, that’s the whole _point_ of using a standardized unit system !), to taste (fuck you, did you put spme in that dish when I ate it in your restaurant or not ?!) and so on.  
This is because professional cooks are universally assholes who don’t want you to succeed and revel in the knowledge that your soufflé is going to be a fucking disaster.

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**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\
**Post date:** [July 12, 2018, 7:21pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/64 "2018-07-12T19:21:34Z")

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> [@Kobal2](#):
>
> And ? 1m = 39.3701 inches = 3.28084 feet. Y’all don’t have an \*\*exact \*\*measure of this specific, arbitrary distance wot my unit system is based on, so yours is pure shite !1!!  
> (I jest, of course, but you get my point, right ?)

That’s exactly why people have trouble converting - they don’t think in metric units, but only convert. We deal in pounds of meat, but when we lived in Africa my mother had no trouble ordering a kilo of meat or half a kilo. You soon learn what a kilo looks like, just as we’ve learned what a pound looks like. We all know what a liter of soda looks like, don’t we? That it is hard to convert from a 12 oz. can to a liter is not important.

In the US we mostly only deal with metric units once in a while. After my daughter lived in Germany for four years she thought in Centigrade temperatures, and know what was hot and what was cold without converting. In chip design we deal in nanometers, and we don’t convert from nanoyards.

As for computers, it is not hard to write a decimal arithmetic package if needed. IBM1620s from the late '50s, early '60s looked like decimal machines. And people seem to be neglecting that changing from pounds to ounces or cups to pints to quarts requires conversion factors for each step, all incompatible, and none derivable from the name of the unit.

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**Author:** ![senoy](https://avatars.discourse-cdn.com/v4/letter/s/dbc845/32.png) [@senoy](https://boards.straightdope.com/u/senoy)\
**Post date:** [July 12, 2018, 7:21pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/65 "2018-07-12T19:21:46Z")

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> [@Nava](#):
>
> How do you give someone’s approximate age? The same expressions are used in Spanish. Couple of examples from Spain: _Hoy hará… veintitantos_ (today it’s… twentysomething). _¿A cuánto estamos? Pues no sé, pero diría que veintimucho._ (What’s the temp? Dunnow but I’m guessing twentylots.) And “under 36” or “over 36” are of course important, that being more or less body temp (actual body temp will vary by person, time of day and health status). _¿Qué hace ahi fuera? ¡Más de 36 y subiendo!_ (how hot is it out there? Over 36 and climbing!)

Really? They just say in the 20s? That’s a huge range. It goes from comfortable at 20 to hot at nearly 30. If you say in the 20s Celsius, it’s not conveying anything. It’s like saying that the temp is between 68 and 86 Fahrenheit, that’s a huge range that will impact my behavior. If the high is 68, I’m going to pack a jacket. If it’s 86, I’m going to bring a fan. In Fahrenheit, the deciles all roughly correspond to a similar temperature range. If it’s the 70s, I know that it’s a comfortable day. If it’s the 80s, I know it’s going to be very warm. If it’s the 90s, I know it’s sweltering. If it’s the 60s, it’s brisk. If you tell me that it’s in the 10s Celsius, it could be a very chilly day to a quite comfortable one. It doesn’t seem to be precise to say it that way.

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**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\
**Post date:** [July 12, 2018, 7:21pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/66 "2018-07-12T19:21:55Z")

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I still don’t understand how computers can more accurately represent traditional units than they can metric units.

The only way this can be true is if you’re allowed to mix units. Feet and inches.

Except if your computer system is keeping track of feet and inches as separate values, how are you performing operations on those values?

I guarantee you that if you’re using traditional units in your computer system, you’re picking one unit and staying with that unit for the whole calculation, because otherwise is madness. You might use feet, but you’re calculating everything in feet, not switching between feet and inches.

If someone inputs 5 feet 4 inches, that’s fine. Now multiply that by 3, divide by sqrt(2), and multiply by a constant.

You’re going to do the math by doing all the operations on 5 feet, and all the operations on 4 inches, and then add the values back together?

Dude, if you do that, then go ahead and do the same thing for thirds of a meter, if it’s that important.

Much more likely you get the input in feet and fractional feet, and do one operation on one value, and output one value. And if so, the length of the unit is arbitrary.

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**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\
**Post date:** [July 12, 2018, 7:24pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/67 "2018-07-12T19:24:57Z")

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> [@Kobal2](#):
>
> Don’t worry boo, metric cookbook writers still use obnoxiously vague “units” like a pinch, a dash, a sprinkle, a spritz, “as needed” (if I knew how much was needed I wouldn’t need to buy a fucking recipe, now would I ?!), a cup (FUCK YOU, that’s the whole _point_ of using a standardized unit system !), to taste (fuck you, did you put spme in that dish when I ate it in your restaurant or not ?!) and so on.  
> This is because professional cooks are universally assholes who don’t want you to succeed and revel in the knowledge that your soufflé is going to be a fucking disaster.

They are just being pre Fanny Farmer traditional, back when all recipes were like that because it was expected girls would be taught to cook by their mothers.

I have lots of British recipe books which give both, and either measure works fine.

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**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\
**Post date:** [July 12, 2018, 7:49pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/68 "2018-07-12T19:49:53Z")

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> [@senoy](#):
>
> Really? They just say in the 20s? That’s a huge range. It goes from comfortable at 20 to hot at nearly 30. If you say in the 20s Celsius, it’s not conveying anything. It’s like saying that the temp is between 68 and 86 Fahrenheit, that’s a huge range that will impact my behavior. If the high is 68, I’m going to pack a jacket. If it’s 86, I’m going to bring a fan. In Fahrenheit, the deciles all roughly correspond to a similar temperature range. If it’s the 70s, I know that it’s a comfortable day. If it’s the 80s, I know it’s going to be very warm. If it’s the 90s, I know it’s sweltering. If it’s the 60s, it’s brisk. If you tell me that it’s in the 10s Celsius, it could be a very chilly day to a quite comfortable one. It doesn’t seem to be precise to say it that way.

😕

My specific examples did not include “in the 20s”, I have no idea where did you read that one.

“Twentysomething” and “twentylots” are two different ranges. One is low 20s (21 to 24), the other is high 20s (26 to 29).

My apologies if my trying to stick close to the original expressions rather than saying we speak exactly as in English (we don’t) confused you.

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**Author:** ![Kron](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kron/32/12444_2.png) [@Kron](https://boards.straightdope.com/u/Kron)\
**Post date:** [July 12, 2018, 9:38pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/69 "2018-07-12T21:38:51Z")

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Fractional meters are not harder to measure than fractional feet just because they are metric/SI. 😕

Anywho, the decimalized form of metric is appreciated by American surveyors… we just use decimal feet for our measurements.

Also, one foot does not equal .3048 meters exactly… it is 1200/3937 meters! For the standard US Survey foot.

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**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\
**Post date:** [July 12, 2018, 9:46pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/70 "2018-07-12T21:46:07Z")

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> [@rat\_avatar](#):
>
> 4 inches vs:  
> 0.333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 M
> 
> 4 inches is **exact** and the metric equivalent is still an approximation.

No. 4 inches is not exact. If you want to be specific, you say 4.0 inches, or 4.00000 inches, or whatever accuracy is appropriate for the situation.

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**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\
**Post date:** [July 12, 2018, 9:54pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/71 "2018-07-12T21:54:06Z")

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> [@scr4](#):
>
> No. 4 inches is not exact. If you want to be specific, you say 4.0 inches, or 4.00000 inches, or whatever accuracy is appropriate for the situation.

In general.

In a number with a decimal point, trailing zeros are significant.

AND

In a number without a decimal point, trailing zeros may or may not be significant.

4 and 4.0 are different by most convention, and that trailing 0 on 4.0 would tend to signify that it is only acculturate to one decimal place, when it would need infinite zeros to capture all of the precision.

So I am going to need a cite that an integer is not an exact value, or that 12 /3 !=4

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**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\
**Post date:** [July 12, 2018, 10:04pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/72 "2018-07-12T22:04:07Z")

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> [@rat\_avatar](#):
>
> In general.
> 
> In a number with a decimal point, trailing zeros are significant.
> 
> AND
> 
> In a number without a decimal point, trailing zeros may or may not be significant.
> 
> 4 and 4.0 are different by most convention, and that trailing 0 on 4.0 would tend to signify that it is only acculturate to one decimal place, when it would need infinite zeros to capture all of the precision.
> 
> So I am going to need a cite that an integer is not an exact value, or that 12 /3 !=4

We are talking about unit of measure. “4 inches” is a physical length, not 4 of some countable object. There is no situation where “4 inches” (or 4 meters, or 4 pounds, or 4 light-years, etc) is treated as an exact number.

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [July 12, 2018, 10:06pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/73 "2018-07-12T22:06:08Z")

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> [@](#):
>
> Quoth **rat avatar** :
> 
> 0.33333 of a meter is an approximation and rounding errors do matter.

4 inches is also an approximation, and a much less precise one than 0.33333 meter.

> [@](#):
>
> Without standard gravity you can’t actually accurately derive the newton (kg⋅m/s), pascal (kg⋅m^−1⋅s^−2), watt (kg⋅m2⋅s^−3) or other units.

Of course you can derive all of those without standard gravity. The kilogram is based on a lump of precious metal in Paris (but they’re working to do away with that), the second is based on the frequency of light emitted by cesium atoms, and the meter is based on the second and the speed of light, and newtons, pascals, watts, and all the rest are derived from those base units. Standard gravity isn’t involved at all.

> [@](#):
>
> This is why banks and other critical users resort to using computationally expensive decimal data types, and why your online loan amortization tool, phone app or calculator never seems to match your statement.

No, banks use ordinary binary floating point calculations if the programmers were lazy and didn’t bother looking up the right way to do it, and binary integer calculations if the programmers did it right. And they don’t care at all about the lack of perfect binary representations of some numbers, because nobody ever cares about that much precision in finance. And if you have a calculator on your phone that disagrees with your bank statement, the most likely explanation is that the app writer was an idiot, and the second-most-likely is that the app is using a different compounding period than the bank is, neither of which has anything to do with the way the numbers are represented.

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**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\
**Post date:** [July 12, 2018, 10:11pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/74 "2018-07-12T22:11:45Z")

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> [@senoy](#):
>
> I’ve never thought about the decile thing. How do Celsius countries do it?

You only do the “decile thing” when you use units where 10 units is a convenient range. You don’t do it with people’s height, for example. You just say “around 5 ft 9”.

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**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\
**Post date:** [July 12, 2018, 10:16pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/75 "2018-07-12T22:16:40Z")

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A cite, from a book that most people interested in this area probably have access to.

A demonstration on why algebraic properties of floating point are neither associative nor distributive can be found in section 4.2.2 of:

The Art of Computer Programming; Volume 2, Seminumerical Algorithms. - Knuth D. (1969)

> [@](#):
>
> Floating point computation is by nature inexact, and it is not difficult to misuse  
> it so that the computed answers consist almost entirely of “noise.” One of the  
> principal problems of numerical analysis is to determine how accurate the results  
> of certain numerical methods will be. A “credibility-gap” problem is involved  
> here: we don’t know how much of the computer’s answers to believe. Novice  
> computer users solve this problem by implicitly trusting in the computer as an  
> infallible authority; they tend to believe that all digits of a printed answer are  
> significant. Disillusioned computer users have just the opposite approach, they  
> are constantly afraid that their answers are almost meaningless. Many a serious  
> mathematician has attempted to give rigorous analyses of a sequence of floating  
> point operations, but has found the task to be so formidable that he has tried  
> to content himself with plausibility arguments instead.

> [@](#):
>
> Several familiar rules of algebra are still, of course, conspicuously absent  
> from the collection of identities above; the associative law for floating point  
> multiplication is not strictly true, as shown in exercise 3, and the distributive law  
> between (x) and (+) can fail rather badly

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**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\
**Post date:** [July 12, 2018, 10:18pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/76 "2018-07-12T22:18:27Z")

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> [@rat\_avatar](#):
>
> A cite, from a book that most people interested in this area probably have access to.

Nobody is arguing that floating point is as exact as integers. We’re just saying we never use integers to represent physical quantities like distance/length. Banking is different, a cent is a countable object (or an abstract concept) and not a physical quantity.

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**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\
**Post date:** [July 12, 2018, 10:22pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/77 "2018-07-12T22:22:26Z")

</div>

> [@rat\_avatar](#):
>
> In general.
> 
> In a number with a decimal point, trailing zeros are significant.
> 
> AND
> 
> In a number without a decimal point, trailing zeros may or may not be significant.
> 
> 4 and 4.0 are different by most convention, and that trailing 0 on 4.0 would tend to signify that it is only acculturate to one decimal place, when it would need infinite zeros to capture all of the precision.
> 
> So I am going to need a cite that an integer is not an exact value, or that 12 /3 !=4

There is no object in the world that is exactly 4 inches long. There might be objects that are 4.0 inches long, or 4.0000 inches long. But there is no such thing as an object that is precisely 4 integer inches long, because measurements don’t work that way.

Again, 4 is a perfectly legitimate number. It’s my favorite integer. And when I say that I have a 4 inch chef’s knife, is that chef’s knife 4 integer inches long?

Of course not, because even if those knives are manufactured with unearthly precision, they are going to vary by some number of atoms, they’re going to expand or contract based on temperature, and so on.

So 4 is not a precise value for the measurement of a knife. It’s a value that means somewhere between 3.5 and 4.5, not something more precise than 4.000000000000000000.

And again, if you need to keep track of integer values for length for some reason, how does the fact that the knife is in inches or feet make it more precise than if it is in centimeters or meters? Yes, you can divide a foot into 12 inches. You can divide a meter into 1/12th of a meter with exactly the same ease.

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**Author:** ![pkbites](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pkbites/32/204_2.png) [@pkbites](https://boards.straightdope.com/u/pkbites)\
**Post date:** [July 12, 2018, 10:23pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/78 "2018-07-12T22:23:44Z")

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I remember back in the late 60’s- early 70’s when I was a kid in school and the push for metrics started in the USA. I was like “you just taught me inches, feet, pounds, etc, now you’re telling me to forget that and do this?” So, yeah, I was resistant. But when I got older I realized our system is based on nothing and doesn’t really make any sense.

what’s really messed up is Puerto Rico. Speed limit signs in MPH, distance signs in KM. WTF?😕

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**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\
**Post date:** [July 12, 2018, 10:34pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/79 "2018-07-12T22:34:43Z")

</div>

> [@rat\_avatar](#):
>
> A cite, from a book that most people interested in this area probably have access to.
> 
> A demonstration on why algebraic properties of floating point are neither associative nor distributive can be found in section 4.2.2 of:
> 
> The Art of Computer Programming; Volume 2, Seminumerical Algorithms. - Knuth D. (1969)

Agreed that doing operations on floating point values can give you trouble if you’re not careful, and when you start with X and divide by Y and then multiply by Y you might not end up with X again, but another number that’s close to X but not exactly the same.

What does that have to do with the metric system? The fact that there is no exact representation for 1/10th in binary? How exactly does it make doing operations on metric measurements harder?

Again, dividing a meter into 10 parts doesn’t give an exact representation in binary. Dividing a foot into 10 parts doesn’t either. Dividing a foot into 12 parts doesn’t either, and neither does dividing a meter into 12 parts. The only fractions that have exact representations in binary are 1/2, 1/4, 1/8, 1/16, and so on. 1/12 doesn’t have one.

Yes, you can represent 1/12, not as 0.00010101… but as one divided by twelve, or 1/1100, and then you’ve preserved your exact representation with integer values. But that’s not a representation of an exact foot divided exactly into exact inches, that’s a representation of one divided by twelve, and if you want to divide a meter into twelve parts you can use the exact same method. Or a meter divided into ten parts.

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**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\
**Post date:** [July 12, 2018, 10:37pm UTC](https://boards.straightdope.com/t/questions-re-the-metric-system/817778/80 "2018-07-12T22:37:25Z")

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> [@Nava](#):
>
> And I’m not sure what do you mean by NTP and STP. In my world those are conditions, not units, and were abandoned decades ago in favor of stating the exact temperature.

Indeed those are conditions, but they were not abandoned in the chemical Engineering world.

When you deal with gases : Hydrogen, Natural Gas, Air, Ethylene, Propylene, Oxygen, etc etc they are bought and sold in volumes not weight and their flow is measured in volumes again.

So a Natural Gas plant in the US will have a capacity of say 1 Million SCFD (Standard cubic feet per day), while the same in China (or Europe) will be 1116 NM3/hr (Normal cubic meter per hour).

Note that it is not just the volume units that need conversion but the reference temperature too. Hope this helps.

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