Poll

How would you perform this calculation in your head?

10,000 - 3,349 = ?

a. intuition
b. math trick
c. systematic mental (pencil and paper in head)
d. pencil and paper

just curious.

at first, i thought i did it intuitively... a very simple common calculation that i do all the time (i always calculate my change when buying something - point of the game? to beat the cashier to it - im kind of OCD about it)... but then slowing down the thought process, i realize i subtract the first 3 digits of 3,349 (3, 3, and 4) from nine and the last (9) from 10...

this is a very common math trick... and if my memory serves me... i did this trick before practicing math tricks for school competitions...

just goes to show that the brain adapts very quickly... it optimizes... its a very impressive little ongoing evolutionary process.
shortest distance between two points? a line... but more specifically a line of length 0... there's always a trick...

quick note on calculating change:
you are always breaking a dollar at some point (assuming you're paying with whole dollars at the time... which i rarely use my change except at the coinstar)
at some point when practicing this you start feeling relative distances when thinking of the digits between 1 and 100.  math can become very intuitive with repetition. lightening fast.  subconscious.
these are probably the easiest and most familiar and common calculations and everyone should be able to do these very quickly...
$1.00 - $0.64 = $0.36...  it pops right in baby.  but it also follows the rules of the math trick above.

not an impressive post whatsoever... im trying to pick apart my brain right now...