Subtracting Decimals

U03_L2_T1_we2 Subtracting Decimals

We need to calculate 9.005 minus
3.6, or we could view it

as 9 and 5 thousandths
minus 3 and 6 tenths.

Whenever you do a subtracting
decimals problem, the most

important thing, and this is
true when you're adding decimals as well,

is you have
to line up the decimals.

So this is 9.005 minus 3.6.

So we've lined up the decimals,
and now we're ready

to subtract.

Now we can subtract.

So we start up here.

We have 5 minus nothing.

You can imagine this 3.6, or
this 3 and 6 tenths. We could

add two zeroes right here, and
it would be the same thing as

3 and 600 thousandths, which is
the same thing as 6 tenths.

And when you look at it that
way, you'd say, OK, 5 minus 0

is nothing, and you just
write a 5 right there.

Or you could have said, if
there's nothing there, it

would have been 5 minus
nothing is 5.

Then you have 0 minus
0, which is just 0.

And then you have a 0 minus 6.

And you can't subtract
6 from 0.

So we need to get something into
this space right here,

and what we essentially are
going to do is regroup.

We're going to take one 1 from
the 9, so let's do that.

So let's take one 1 from the
9, so it becomes an 8.

And we need to do something
with that one 1.

We're going to put it
in the tenths place.

Now remember, one whole
is equal to 10 tenths.

This is the tenths place.

So then this will become 10.

Sometimes it's taught that
you're borrowing the 1, but

you're really taking it, and
you're actually taking 10 from

the place to your left.

So one whole is 10 tenths, we're
in the tenths place.

So you have 10 minus 6.

Let me switch colors.

10 minus 6 is 4.

You have your decimal right
there, and then you have 8

minus 3 is 5.

So 9.005 minus 3.6 is 5.405.