Comments on: Can you Name this Mathematical Phenomenon?

By: San

San — Fri, 23 Oct 2009 14:13:12 +0000

10^2 =100
0.1^2 =0.01 (without the decimals they are opposite)

20^2 =400
0.2^2 =0.04

22^2 =484 (which is the same way each way)

interestingly

33^2 =1089
99^2 =9801

haven’t found one exactly like yours though. I know that there is a name for this time of number but I don’t recall what it is lol.

By: mitch

mitch — Thu, 17 Sep 2009 13:56:58 +0000

Has anyone identified what this these numbers are called? I ran a few, results here http://pastebin.com/f2dd94ad6 and found many interesting patterns.

Professor Homunculus sez:

Not so far, but your results are pretty interesting. Thanks for doing that.

By: MS Witham

MS Witham — Wed, 11 Mar 2009 03:19:43 +0000

I think what you have encountered is known as the rule of 9′s… this is a common reconciliation tool used by geeky accountants to identify a transposition of numbers! But it does seem to be at the base of your math… let me know ;-)

Professor Homunculus sez:

I don’t think that’s it. “The Rule of Nines” is a catch-all name for many of the very cool and useful things you can do with nines, one of them being a divisibility rule for 9 (which is the basis of the geeky accounting trick), all of them having to do with modular arithmetic in base 10.

One or more of those things may have something to do with this phenomenon, but that’s not the name of it. Would be interesting to see how Mod 9 fits in with it, though.

Thanks for the input. If you can figure out what the rule of nines has to do with the above phenomenon, please send it in. I’d be interested to see it.

Still looking for the name of this puppy, though.