
Mental Math Shortcuts
I have always been a user of math tricks and techniques. I
have nothing against using a good calculator, but doing mathematics
in my head is good brain exercise. It also is nice to have the
ability to add, subtract, multiply and figure the sales tax on
that new television without a calculator, since most of us do
not carry them around everywhere we go.
There are intensive programs that can teach you how to do
mental math using shortcuts that make it possible even to multiply
fourdigit numbers without paper or pencil. Following this short
piece you’ll find a recommendation for one that isn’t
so intensive, but is very practical. But just to give you an
idea of how easy it is to do math in your head, here are a few
examples.
Let’s start with something easy, like multiplying 342
by 11. One way to make a problem like this easier is to start
with 342 multiplied by 10, which most of us can quickly see is
3420 (just add a zero). Now, if we add one more 342 to that,
we have the result for 342x11, which is 3,762. That wasn’t
too difficult, was it?
That is a simple example of a shortcut that makes mental math
possible. Now, what if we want to find the sales tax on a $680
couch if the rate is 6.5%? That might seem a bit trickier, but
there are shortcuts for these types of problems as well. Star
with 6% of $600. That’s easy enough, being just 6 times
$6, or $36. Keep that figure in mind and add to it 6% of $80,
which is just 60 cents for each ten dollars, or $4.80. Now we
are at $40.80, and we just have to add .5% to that for our total
tax.
For this last step, think of 1% of the total price, which
is easy figure: $6.80 (move the decimal two places to the left
to get 1%). Now just cut that in half, which should also be relatively
easy, to arrive at $3.40. If you are still holding that $40.80
in your mind, add the $3.40 and you have $44.20 in total sale’s
tax. I is easier than you might think once you practice a bit,
and if you have a scrap of paper, you might take notes as you
go  without having to write out the whole equation.
If you are interested in helping others learn mental math
or other learning skills consider a masters
for teachers.
