Speed Math
OK, so I don’t go anywhere without my Palm, which has more calculator than I’ll ever need . Still I find myself yearning to teach myself all the speed arithmetic techniques of the Trachtenberg Method, also described briefly here .
Addition
The method advocated here involves the following principle: “Never count higher than eleven.” If any running column total exceeds 11, subtract 11 and put a tick mark in that column. When you reach the bottom, write down the running total, and under it write the number of tick marks. Now add these two rows using the strange rule of adding the two numbers in any column and the neighbor tick number. Write down the last digit and carry the other digit, if any, working right-to-left.
Example
3 6 8 9
7' 5' 8'
9' 6 6 7' column
1 0 6' 4 of
6 4' 9' 8' figures
----------
8 1 1 3 running totals
1 2 3 3 ticks
----------
2 '1 6 7 6 sum
This technique works on arbitrarily long columns of figures, and the columns can be dealt with in any order desired, except at the very last step.
Two words: dead batteries.
Posted by Mike Jones on October 4 2003 21:35
If I'm so far away from civilization that I've let my Palm die, I doubt needing to being able to do arithmetic faster than I already can would prove a pressing problem...
Posted by Zed on October 5 2003 10:39
I got seriously into the Trachtenberg stuff when I was in high school. Not so useful any more, but I still remember and use a few of the tricks, and can, for example, still square a two-digit number in my head, or at worst, quickly jotting a few numbers on a scrap of paper.
35 squared =
25 (= 5 squared)
30 (= 3 x 5 doubled)
09 (= 3 squared)
____
1225
68 squared =
64 (= 8 squared)
96 (= 6 x 8 doubled)
36 (= 6 squared)
____
4624
Posted by Scott on October 5 2003 10:59
Damn, those examples got screwed up by the lack of spacing in HTML.
35 squared =
..25 (= 5 squared)
.30 (= 3 x 5 doubled)
09 (= 3 squared)
____
1225
68 squared =
..64 (= 8 squared)
.96 (= 6 x 8 doubled)
36 (= 6 squared)
____
4624
Posted by Scott on October 5 2003 11:01