Wikipedia:Reference desk/Archives/Mathematics/2010 January 30

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January 30

percentages,round offs and number based systerms

Please, I will like to know how any of the topics above can help in the world of business and how it can help solve problems in either sports,health,fishiries and it's economic importance to a country. —Preceding unsigned comment added by Ericasante (talk • contribs) 11:25, 30 January 2010 (UTC)

Perhaps you should ask this question at Wikipedia:Reference desk/Miscellaneous; this question does not really require much mathematics to answer, depending on the sorts of responses your expect (you will receive responses here, of course, but you will probably receive a greater number of responses at the miscellaneous reference desk). In the context of this question you might like to see financial mathematics, but in any case, most school mathematics textbooks should give you some indication of how to use these concepts in the "real world". As for the much deeper mathematics in economics, you might like to use calculus, or even the theory of manifolds. Thus you should realize that the mathematics in economics is far deeper than "percentages, round offs and number bases systems"; it can involve, for instance, Ergodic theory and Stochastic calculus. --PST 12:04, 30 January 2010 (UTC)

could there be ANY change made in the rules of logic without immediate inconsistency?

Could there be any, even the slightest change in the fundamental laws of logic without the new logic being totally inconsistent - you can prove anything and its opposite. Thanks. 84.153.213.154 (talk) 14:07, 30 January 2010 (UTC)

Yes. There are many different formal logical systems. Algebraist 14:10, 30 January 2010 (UTC)

See Non-classical logic. Buddy431 (talk) 16:27, 30 January 2010 (UTC)

Doublethink and Cognitive dissonance indicate being able to prove anything and its opposite should pose no problems :) Dmcq (talk) 16:44, 30 January 2010 (UTC)

Hexadecimal

Why large hexadecimal numbers are converted into negative decimal numbers on a calculator?--Mikespedia (talk) 14:22, 30 January 2010 (UTC)

Because of a bug in the calculator, probably related to an overflow when the number gets bigger than can be stored in the number of bits available. What calculator is it? Can you give an example of a hexadecimal number and the negative decimal number it gets converted to? --Tango (talk) 14:44, 30 January 2010 (UTC)

It could be it's using a particular signed integer representation. E.g with 32 bit signed integers the largest number that can be represented is 2^31 - 1, the smallest is -2^31. But if you represent the numbers as hex you get

2^31 - 1 = 0x7fffffff

-2^31 = 0x80000000

i.e. hex numbers larger than 0x7fffffff represent negative numbers. There's a little info here, more here (it uses binary but the same can be applied to hex)--JohnBlackburne^words_deeds 15:34, 30 January 2010 (UTC)

See Calculator#Mechanical_calculators_reach_their_zenith. Old mechanical calculators had a fixed number of decimal digit positions but no sign. Zero was represented by 00000000 and one by 00000001. Subtracting one from zero gave 99999999, which thus represented minus one. So negative numbers were represented in the same way as large numbers. This convention was herited by electronic computers having a fixed number of binary digit positions but no sign. Bo Jacoby (talk) 17:45, 30 January 2010 (UTC).

The hex calculators are probably using Two's-complement arithmetic since that's what most computers use. Of course that means they have to operate at a specific (maybe user selectable) word length. 66.127.55.192 (talk) 20:17, 30 January 2010 (UTC)