"Lane" lane (no spam) at copperaccents dot com wrote in message
...
On the plus side, you could do many three significant figure
calculations
(OFTEN 'good enough') as fast or faster than with a modern calculator,
and
RARELY made the common 'multi-order of magnitude' mistakes that now
plague
our students. They just don't THINK. Whatever the calculator says, they
take as gospel. We see 'em calculate the size of some sub atomic
structure
such that it wouldn't fit between the Earth and the Moon! Garbage in,
garbage out ... but FAST, and to ten figure accuracy. Ignorance is
bliss.
The concept of the quick, in your head or on paper, order of magnitude
calculation is all but lost.

Dan Mitchell
============

For example, I was taught by one high school teacher to estimate in your
head first then use the slide rule or calculator for a final figure. For
example if you're multiplying 11.31 x 36.416, first estimate in your head
10
x 36 = 360, then your answer can't be anywhere near 3600 or 36 or 360000.
That helps a lot.


I had a Physics Prof that use to do calculations in the blackboard, then get
one of us in the class to work out the figures with a slide rule while he
mentally calculated the answer. He was an eccentric old chap and while he
calculated he wiggled his hand in a circular motion,sometimes clockwise
,sometimes counter clockwise. Turned out he had used a mechanical
calculating machine during the war and still mentally twisted his hand
forward or back according to whether he was multiplying or dividing.