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it's hardly practical. Yes, interesting, but I would not use it at all. The way I know how to do multiplication "manually" is superior than this. You line up numbers on top of each other. Then you start multiplying first digit of the bottom number with all the digits of above number, from right to left and adding any carry over. You start writing the result on the same column you are multiplying. Then you add them all.

    123
    123 
  x______
    369
   246
  123
+________

  15129
That's what I learned in elementary school and have been using since then. It's interesting to know how others to do it.



> That's what I learned in elementary school and have been using since then. It's interesting to know how others to do it.

well, i generally do it using a 'covolution approach' like this:

     45
   x 86
   ------
       0 (5*6 == 30) -> take the units place, and put '3' as carry over
      4  (6*4+8*5+3 == 47) -> take the units place, and put '4' as carry over
    36   (8*4+4 == 36)
-------------

   3640
-------------

with sufficient practice, you can multiply arbitrary 3 digits in approx 10-15 seconds or so ;)

[edit-1]: my formatting sucks, cannot seem to align stuff nicely at all.




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