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Re: Stupid Arithmetic Tricks



also sprach Branden Robinson <branden@debian.org> [2002.03.28.1831 +0100]:
> If I'm given a long column of one or two-digit numbers to add up (on
> paper), I go down the ones column and strike out all complementary pairs
> that add up to 10, e.g., 1 and 9, 2 and 8, 3 and 7, etc.  For each pair
> that I strike out, I make a tally mark or just keep track mentally.
> Odds are you won't be left with very many digits to add up.  So you do
> that, carry the one if need be, and then add your tally marks to what
> you're carrying.  So if I struck off 4 complementary pairs that add up
> to 10 and I was carrying a one, I'm now carrying a 5.  You can then
> repeat this process for the tens column.  In theory this works for
> arbitrarily long numbers, but with numbers > 99 paper space becomes a
> concern.  This technique is much, much faster than manually adding each
> digit to the one below.  At least in my experience...

not meaning to push you off your cloud, branden, but that's how it's
taught to first-graders over here in germany ;)

-- 
martin;              (greetings from the heart of the sun.)
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