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First, you need to know how to multiply a number by two
Well, multiplying a number by 2
is actually adding this number to itself
The other thing you need to know
is to divide
a number by 2
This, well, there’s no really
other way than to know
how to do it just bit by bit
Well, with a little bit of practice it’s kind of
easy and fast.
And also you don’t have to mind all the halves that you can get like when you
divide 7 by 2
just put 3, don’t care about
3.5 and 3½
It doesn’t matter, Just put 3.
So that gets something rather
simple. Now, let’s see
the rest
of the procedure.
Let’s take an example with
27
27 × 13
What you do here
is to put numbers in two columns.
27 on the left
And 13 on the right.
On the left column,
you’re going to multiply
by 2
so 27 + 27
Yes, it’s the same
That’s the same number.
7 + 7 = 14
You get 54
Here, you divide by 2.
So, what multiplied by 2 makes 13?
Of course it’s 6.5
6.5
But as I said a little while ago,
you don’t care
you don’t mind
you just
get rid of this .5
Nobody cares about it.
Next step, you just continue: You multiply by 2 and you get 108.
Here, you divide by 2
I forgot to write it down here. OK Or I can write it this way.
You divide by 2
6 ÷ 2 = 3
And we continue once more
It’s kind of easy
And here you divide by 2 again.
3 ÷ 2 = 1.5 but we keep only the 1
and we don’t care about all the decimals.
So, we’ve arrived at this
point where we have
a 1 on the right column.
It means STOP.
So you stop here.
We’re almost there.
Now we have to go to the step number 2.
Step 2 is very easy.
On the right column
you just find all the EVEN
numbers.
Here, there’s only one.
Only one even number which is
6
What you do with this 6,
you just remove it
and you remove
the number
on the left column
just at the same line
So, since 6 and
54 are on the same line you remove both of them
There is no even number if there would
be any more, you would do that with
all of them
Now what you do
is very very simple because we are done with everything.
You just have
to add up
all the numbers
remaining,
not the 54,
all the numbers remaining on the left column
which makes…
Well, let’s think about it
Something like
6 + 8
+ 7
= 21
2 + 1 + 2 = 5 and finally 2 + 1 = 3
351
And believe it or not
27 × 13 = 351
I didn’t use any
I didn’t use any
multiplication table to make this multiplication.
OK, there’s a little tip here:
It’s to put the smaller number
in the right column to finish earlier Here we have 27 and 13
It’s better to put 13 here because since you divide
if it’s the bigger number
you put it’s gonna
make lots of lines
That’s a little tip.
You can do that with any number and
it always
works
You don’t need to know any multiplication table.
If you wasted time
in your childhood to learn them
well, too bad
NO, I’M KIDDING!
OK, bye, bye!