====== 2021-01-02 - times tables ======

when i was in primary school, there was a time i was tasked with memorizing (!) a matrix of 10x10 (not so) random values, with their exact positions -- aka: times table. no way -- it never worked for me this way. memorizing (i.e. hardcoding into brain) that much stuff was out of the question. but i still need to pass an oral exam out of it... so... why not just multiply it fast enough, so that no1 will notice((or at least won't be able to complain))? and so i did. yes -- i never learned times table. over time i did remember some random elements of it, but vast majority i was just multiplying on the fly. to do so i developed some simplifying algorithms, like:
  * multiplying N*5 is N*10/2
  * multiplying N*9 is N*10-N
  * etc...

the 2nd "rule" was a bit exceptional for me, as it was just an observation at that point. when i've noticed this property i was happy as it knocked out a full line of multiplications with it. i was even happier when sometime later i came up with a formal proof of it. after all 9==10-1, thus N*9 is N*(10-1) which in turn is N*10-N. generally simple stuff, but having barely 2-digits of age it was like discovering what dark matter is. i think it was one of those rare moments in education, when given a (yet another) really brain-dead task turned out to be a positive thing -- overall fun and insightful process. and btw: why it was not presented as such a task in a first place?

anyway -- somewhere last month, while listening to [[https://festivalofthespokennerd.com/podcast/|a podcast of unnecessary detail]], namely [[http://festivalofthespokennerd.com/podcast/episode-05-table/|the tables episode]], i learned that [[https://www.youtube.com/user/steventhebrave|Steve Mould]] did exactly the same when tasked with memorizing times table. it was comforting there are more ppl who utterly hate / can't memorize stuff if it is not well understood first. high five! :D