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How to do 1296 Division Quickly and Accurately
Posted By: Jake Jacobs
Date: Sunday, 18 October 2015, at 3:48 a.m.
In Response To: How to do 1296 Division Quickly and Accurately (RobertFontaine)
In 1960, when I was in first grade, a translation of Jakow Trachtenberg's system was a modest bestseller. Trachtenberg was a concentration camp survivor who had kept his sanity by working out algorithms for doing rapid multiplication. To multiply by 11 you started from the left with the first digit and then built your answer by adding adjacent digits, ending with 1* the last digit. For example"
432417 * 11 = 4 and (4 + 3 =) 7 and (3 + 2 =) 5 and (2 + 4 =) 6 and (4 + 1 =) 5 and (1 + 7 =) 8 and 7, that is: 4756587. You had to be alert to carrying a 1 whenever that was necessary, but otherwise it was completely straightforward.
My dad taught me the algorithms and would trot me out as a party trick, pitting me against grownups. I had one advantage going in: an exceptional shortterm memory. And since I was retarded when it came to writing I had no temptation to use a pencil and paper. Thus, when he would call out "623842" Aunt Babe (who was teaching second graders, "big kids" to me) would just finish writing that down when I'd sing out: "6862262!" Along about the third time this happened Aunt Babe would snap her pencil, then try to stab my dad with the shards.
Sibling rivalry can be a bitch.

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