Posted By
Lavina
on 2007-01-11
05:15:18
 |  Re: LOL maths
Last night I remembered, that several years ago (7-8) I began to wonder about this again. Then, I made an equasion to find out why this worked. So I made something like this:
10x+y-(x+10y)=9x-9y=9(x-y) where abs(x-y) ={1->9} So actually the result of the original substraction is the simple multiplication table of 9...  I also found out in primary school, that this multiplication table of 9 (when multiplying 9 with an 1 digit number) works like this: 9*x = ZQ where the two digits of the result are Z and Q; Z=x-1 and q=10-x / So in decimal the result is 10*(x-1)+10-x=9*x /
So I got stuck at this point 7-8 years ago. Sadly, they did not mention this phenomena on accounting seminars at the uni.
Cheers Mike! 
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