Posted: 9/30/2011 7:53 AM
Post subject: Kinda Weird Math Question
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Tanooki_Teabag
Player (200)
Joined: 1/24/2011
Posts: 108
It seems like there are quite a few people here with knowledge of mathematics, so I figured this would be a good place to ask this: is there a generally accepted way to denote an individual digit's place? For example, I want to add the tens digit and the ones digit of 18 to make 9. What would be the proper way to write that sort of thing out in a formula? Right now I'm using x0 and x1, but if there's a more intuitive way to write it I'd be interested in knowing.
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Posted: 9/30/2011 8:06 AM
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Dacicus
Editor, Player (67)
Joined: 6/22/2005
Posts: 1042
I've seen and used subscript notation for that purpose. You can see an example here.
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Posted: 9/30/2011 6:47 PM
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DrJones
Joined: 4/3/2005
Posts: 575
Location: Spain
If you plan to repeat the operation on the result until the result is a one digit number, that's equal to performing the operation mod 9 on the original number. Otherwise, every number of Y digits can be defined as x1 * 10^(y-1) + x2 * 10^(y-2) + x3 * 10^(y-3) + ... + Xy
No.
Posted: 9/30/2011 8:59 PM
Post subject: Re: Kinda Weird Math Question
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Tub
Joined: 6/25/2005
Posts: 1377
Tanooki Teabag wrote:
is there a generally accepted way to denote an individual digit's place?
No, since "digits" are not an inherent property of numbers. That we're talking in base10 is a social convention, not a mathematical one. Usually, if you're interested in digits, you'd formally introduce (and name) the base10 representation first. Something like this: Let: a = \sum_{i=0}^{\infty} a_i * 10^i, 0 <= a_i <= 9 be a number and its base10 representation. Whether you use ai or ai or a(i) or a[ i] or something else is up to you.
m00
Posted: 10/1/2011 1:15 AM
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IronSlayer
Joined: 5/30/2007
Posts: 324
Yes, Tub is correct; there is no standard notation for this. If you choose to write a number as a sum of powers of ten ie the standard base 10 representation, as Tub noted, it should be possible to convey what you're trying to do, but there is no special notation.