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Welcome to the Student Academic Learning Services video on dividing decimals.
In this video we're going to look at how to divide a decimal number by another decimal
number.
On the left hand side of the screen we have our examples.
And on the right hand side we have our method.
Divide, multiply, subtract, bring down.
So, our first example is 0.6 divided into 16.44.
Now we don't really want to divide by a decimal here because
it gets needlessly complicated, so what we can do is we're
going to multiply both the divisor and the dividend by 10.
What that's going to do is move that decimal place over.
So we get 6 divided into 164.4, a number much easier to divide.
And the reason we do this, or we can do this,
so we take a fraction and we can multiply that by anything
as long as we're multiplying the top and the bottom by the same thing
the fraction remains equivalent to one another.
Two thirds is the same as 20 over 30,
just the same as one half is equal to two fourths, is equal to
1000 over 2000. They'll all give us the same decimal number.
So, knowing that, we can perform this division.
And I don't really like to work with this as this is kind of getting muddied up there
so we're just going to re-write our new question. 6 into 164.4.
So our first step is going to be to write that decimal up there.
Now 6 won't go into 1 obviously,
so we're just going to put a 0 there to hold its place.
6 divides into 16 twice, 2 times 6 is 12, 16 subtract 12 gives us 4
and we're just going to bring down that 4.
6 divides into 44, 7 times, 6 times 7 is 42, 44 subtract 42 gives us 2,
and we're going to bring down one 4.
6 divides into 24, 4 times and 4 times 6 is 24.
Subtract those and we get 0, so we're done.
So 6 divides into 164.4, 27.4 times, and if you punch it into your calculator
0.6 will divide into 16.44, 27.4 times.
If we multiply it by 100 up here we'd get 60 dividing to 1644 and it would go in 27.4
times.
So just experiment a little on your own with your calculator and a scrap piece of paper
and try some different examples; you'll see that no matter what you do,
as long as you're multiplying this by 10 or 100, 1000, 1 000 000
or whatever you're doing, as long as you do it the same to this number,
you'll always get the same answer.
Let's move on to our second example,
we have 0.78 divided into 21.45.
Now, we're going to multiply by 100 here, on both sides,
so that's going to move the decimal place over two spots.
And again I'm just going to re-write this because it just
makes it a little easier to work with, and our decimal is here now.
So we're going to write our decimal up there first, just to keep things organized.
78 won't go into 2, nor will it go into 21.
It will go into 214 however, it will go in twice.
2 times 78 is 156. We subtract 156 from 214, we get 58, and we bring down the 5.
A little note here, you might need to use a trial and error method if you're
not using a calculator, and that's fine, just do it on a scrap piece of paper on the side.
So, 78 goes into 585, 7 times. 7 times 78 is 546,
and when we subtract 546 from 585 we're left with 39.
We're going to add a 0 and bring that down.
Again, we can add zeros all across the page if we want
because adding those zeros isn't going to change anything in our number here.
2145 is the same as 2145.00000.
So, 78 divides into 390, 5 times, and 5 times 78 is 390.
You subtract those and you get 0, so we're done here as well.
So 78 divides into 2145, 27.5 times or 27 and a half times,
And 0.78 will divide into 21.45, 27 and a half times.
So again I showed you two examples here.
I encourage you to try some other examples.
You can come up with an infinite amount of questions for this.
You could do four decimals, you know 0.0005 divided into, I don't know,
114 416 and just see what type of number you come up with.
You can come up with a, like I said, infinite amount of examples,
just pick some numbers and start dividing.
If you have any questions with the method that we used here or
how we calculated anything in here, I encourage you to come
to the SALS centre, located in room 204 of the Student Services Building,
and make an appointment with the appropriate Learning Skills Advisor.
Thanks for watching.