Wikipedia:Reference desk/Archives/Mathematics/2006 November 17

= November 17 =

Transportation problem
It is surprising to see that there is no wiki for such a famous problem. Could some one please create one? "Assignment problem" also needs cleanup. I need to study these problems, not at a detail level which would ofcourse require a text book. A wiki with usual depth will suffice.

Thanks and regards,


 * Did you have a look at Transportation theory? Welcome to Wikipedia, the free encyclopedia that anyone can edit. If you can improve Assignment problem, you're welcome to do so. --Lambiam Talk  10:11, 17 November 2006 (UTC)


 * The article on Transportation Theory doesn't even consider an algorithm to solve the Transportation Problem, whereby goods are to be sent from several sources to several destinations at minimal total cost. A common one is to use Vogel's Method to get a good initial solution, then improve this by successively replacing one route in use by another not in use. The process is similar in concept to the basic iteration done in the Simplex Method for general linear programming, but done within a table whose rows and columns represent sources and destinations, and whose cell values are the flow along that particular route.


 * In fact, the article seems to be ludicrously abstract and essentially useless in its present form.81.151.247.61 21:07, 19 November 2006 (UTC)

US - Imperial measurements
How come fluid ounces are different in US customary measurements to those in the Imperial System, when both are based on the density of water? Both measurement systems use the same ounce, and the density of water is pretty much the same globally, ignoring slight changes due to temp/pressure. La  ï  ka 10:05, 17 November 2006 (UTC)


 * I would guess it's salt fresh water versus ocean water, which have different densities. StuRat 10:34, 17 November 2006 (UTC)


 * I guess you meant fresh water vs. ocean water. :-) CiaPan 11:29, 17 November 2006 (UTC)


 * No; even if one was sea water, the measures are still out. They would be closer for brine, but brine seems like a slightly odd choice, given that pure water would be more practical. La  ï  ka  16:19, 17 November 2006 (UTC)


 * Who said practicality had anything to do with imperial/customary units? Let's not forget the ugly Fahrenheit scale that use some bizzare value of uncertain origin as it's 0 point Nil Einne 17:31, 20 November 2006 (UTC)

Actually, while the Imperial fluid ounce was based on the density of water (at 16.7 °C), the US fl.oz is derived from the US gallon, which is a volume measurement defined as 231 cubic inches. Thus the Imperial gallon and US gallon have entirely distinct operational definitions. (Well, not any more, now that both are defined in terms of SI, but they used to.) EdC 00:06, 18 November 2006 (UTC)


 * This begs the question of when and why the two countries went their separate ways. The article on gallon offers some background. --KSmrqT 10:40, 18 November 2006 (UTC)