Wikipedia:Reference desk/Archives/Mathematics/2016 May 5

= May 5 =

Percent deviation from additivity
(Removed in favor of the duplicate question on the science desk. -- BenRG (talk) 17:42, 5 May 2016 (UTC))

As I see no response there I do not consider the reason for removing the question here on reason of apparent duplication to hold. It is not really a duplication since the question has a more mathematical status. It seems that no one at the Science Refdesk had the initiative to address the issue. I'll restore it with additional detail also .--85.121.32.1 (talk) 15:21, 6 May 2016 (UTC)

What is the quantitative expression associated to the verbal phrase +/_x % deviation (expansion or contraction) from the addivity of volumes in water ethanol or water salt/sugar solutions?--85.121.32.1 (talk) 15:47, 5 May 2016 (UTC)

Could it be a fraction whose numerator include the difference between the volume of the mixture V and the volumes of the two components V1 and V2 and the denominator equals the sum V1+V2:

$$\%\Delta V_r= \frac{V-(V_1+V_2)}{V_1+V_2} 100$$?--85.121.32.1 (talk) 15:52, 5 May 2016 (UTC)

or $$\%\Delta V_r= \frac{V-(V_1+V_2)} 100$$?

Which one of these two variants of this fraction which can be called relative volume difference are more appropiate?--85.121.32.1 (talk) 15:15, 6 May 2016 (UTC)
 * I think it's really a matter of interpretation but I would probably use the first one, though they both evaluate to the pretty much the same thing in actual situations. See Relative change and difference if you want to be confused even more. To me this falls into a grey area between math and language; once you have a formula the math is just a matter of calculation, but words have different meanings depending on context so there can be more than one correct way to turn them into a formula. --RDBury (talk) 19:14, 6 May 2016 (UTC)