>> Hi, this is Julie Harland
and I'm YourMathGal.
Please visit my website
at yourmathgal.com
where you could search for any
of my videos organized
by topic.
On this video,
I'll show you how
to divide decimals
by whole numbers
and round the answers
when necessary
to nearest hundredths.
So we do the following five
problems on this video.
All right, we're going
to continue dividing
with decimals.
In this video,
we'll take a decimal number
and divide it
by a whole number.
Previously, we did problems
where we were changing
fractions to decimals.
So it's a whole number divided
by a whole number
but our answer was written
as a decimal.
And we've done whole number
divided by whole numbers
where we round it.
So, now we're going
to take something
that already is a decimal
but we're dividing
by a whole number.
So for this problem,
which is similar,
we just put the 21 into 118.2
and we just divide as usual.
The only difference is as long
as it is a whole number here
we're going
to put the decimal point right
up there.
So let's go ahead
and try that.
So we have to think,
how many times does 21 go
into 118?
Let's see,
I think 6 is too big.
I'm going to try 5.
Let's see 5 times 21 is 105
and that is 13, and we bring
down the 0.
All right, and then we have
to see how many times does 21
go into 130.
I think that's going to be 6.
6 times 21 is 126.
And then 21 into 42 is 2.
Now, as far
as just knowing how many times
it goes in and how
to do long division,
I'm not covering how
to do long division
on this video.
You can do
that with whole numbers
and then you just apply it.
Except the only difference is
you're putting the decimal
point here.
So this comes out exact,
the answer is 5.62.
To check the answer,
you multiply.
21 times 5.62
and you could use any strategy
you want to multiply
or you can use a calculator
to check, if you're just doing
your homework, and actually,
that it equals 118.02 exactly.
All right,
let's have you try one.
All right,
so try this problem.
Put the video on pause
and try it on your own.
Okay, so we're going to start
out the same way.
[ Pause ]
So the only difference is
as long as this is a whole
number over here, we're going
to put a decimal point,
above where the decimal point
is and do our
regular division.
So 13 goes into 30 twice.
[ Pause ]
All right and then 13 goes
into 40, three times.
So 3 times 13 is 39.
Then bring
down the left digit here.
Remember, all you're doing is
bringing down the next digit
each time and that's 1,
and it goes in evenly,
so this answer is 23.1.
And again, we just check
by multiplying 13 times 23.1
using any strategy you want
and you end up with 300.3.
I'm not going
to show the multiplication
here, but remember,
you just multiply 13 times
23.1 and we--
I mean, by 231
and move the decimal
in one space.
So in both of these problems,
we ended up with zero
as a remainder.
That doesn't always happen.
So let's do one
where we're going
to have to round.
All right,
so let's do this problem.
So let's divide and round
to the nearest hundredth.
So we begin by dividing 7
into 23.2.
And remember,
we want to make sure this
number over here
on the left is always a whole
number, and then we need
to put the decimal point
up here.
Now, it says to round
to the nearest hundredth.
So that means we need to go
out to the thousandths place
to round.
So right now,
there is only one place
after the decimal point
so that's a tenth,
so you should put a zero
for the hundredth
and the thousandth.
And that as far as we're going
to go out,
so that we could round the
answer to the hundredth,
and then we just divide
as usual.
So we have 7
into 23 goes three times.
We bring down the next digit.
7 goes into 22 three times.
And again we subtract.
Bring down the next digit.
7 goes into 10 once,
and then we bring
down the next digit.
And 7 goes into 30 four times.
You don't really have
to subtract at the end.
What matter is
that this is a 4,
now we're going
to decide whether we're going
to round, up or down?
So since this is a 4,
less than 5,
we don't round that.
So we're going
to keep this as 3.37.
So the answer is
approximately, right,
not exactly equal to 3.31.
Now, let's go ahead and check
to see for if we are close.
[ Pause ]
So if we do 7 times 3.31
and you could this any method
you want.
I'm using a calculator.
I have 23.17
and so the question,
is that close?
So that's close.
So it seems reasonable
that 3.31 is possibly the
right answer.
Okay, 'cause 23.17 is close
so you could think
of this as 23.20.
All right, here is one
for you to try.
5.2 divided by 11.
See if you can guess what the
answer is going
to be close to.
This is sort of like 5 divided
by 11 or 5/11.
That seems like about half.
So we know our answer is going
to be less than one.
All right, so put the video
on pause and try this
on your own first.
Okay, so we have 11 into 5.2
and we're going to round
to the nearest hundredth.
So remember,
we want to go three places
after the decimal so we
that we could round
to the hundredth.
There's a whole number
over here, put the decimal up,
and then we do our division.
11 goes into 52 four times.
4 times 11 is 44 and subtract.
Bring down the next digit.
11 goes into 80 seven times.
So 7 times 11 is 77.
And subtract
and then we have 11
into 30 goes two times.
So, the question is what does
it round to?
Since the thousandths place is
a two, right?
With 0 through 4,
we don't round that.
We keep it as is.
The answer
to this is approximately 0.47,
or of coarse,
you could put a 0 in front
of the decimal point.
And it's always a good idea
to just-- and remember how I
kind of estimated it
that it was about a half.
You know, 0.47,
that's close to 0.5.
So, it seems
like a reasonable answer.
So let's just check,
what 11 times 0.47
and that's going to be 5.17,
so it's actually pretty close
to 5.2.
All right, here is one more
for you to try.
12.23 divided by 6,
we're going to round
to the nearest hundredth.
So put the video on pause
and try it on your own first.
So let's do 6 into 12.23,
put the decimal up
and just do regular division.
6 into 12 goes twice.
Remainder 0,
bring the next digit down,
and here is where a lot
of people have trouble.
6 does not go into 2
at all right, it's bigger.
So remember to put
to a 0 here.
Now, you could go 0 times 6
and subtract or once you
to put the 0 there,
and you could just now bring
down the next digit.
Let's see what will happen
at the next place.
And then 6 goes into 23.
It goes three times, right?
Now, remember, we're going
to the nearest hundredth,
so I wanted to go three places
after the decimal point.
So here, I just have
to add the one zero
to get three places
after the decimal point
and bring that one down.
So 6 goes into 50 eight times.
So now I can round.
All right, 8 is five
or bigger, so this rounds up.
So instead of 2.03,
it will be 2.04.
So it's approximately 2.04.
And let's just do a little
check, what is 6 times 2.04?
I think that's 12.24.
You could to that
without a calculator.
And again,
it's close so it seems
like a reasonable answer,
right?
12.24 is close to 12.23.
It's close.
All right,
so on the next video we're
going to show how
to divide decimals
when you're dividing
by a decimal.
So-- so far,
we've only divided
by whole numbers.
[ Silence ]
Please visit my website
at yourmathgal.com
where you can view all
of my videos
which are organized by topic.