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## Subtracting decimals: standard algorithm

# Subtracting decimals: 39.1 - 0.794

CCSS.Math:

## Video transcript

Let's try to calculate
39.1 minus 0.794, and so pause the video
and try this on your own. All right, I'm assuming you've
given a go at it, so now let's work through it together. So I'm going to rewrite this. It's 39.1 minus-- I'm going to
line up the decimals so that I have the right place values
below the right place values-- minus-- this
0 is in the ones place, so I'll put it in the
ones place-- 0.794. And now we're ready to subtract. Now, how do we subtract
4 from nothingness here, and 9 from nothingness here? Well, the same thing
as nothing is a 0. And so now we can start to
think about how to subtract. Well, we still have the problem. Well, we're trying
to subtract 4 from 0, so we're trying to
subtract 9 from 0. So what we could do
is take this one tenth and try to regroup it
into the hundredths place and the thousandths place. So let's think about this. If we make this-- actually
that's not actually going to solve our problem. Well we could do
it, but then we're going to have zero
tenths, and we're still going to have a problem here. So actually let me
go to the ones place. So let me get rid
of a ones, so that's eight ones, which is
going to be 10 tenths. So that's going to now--
we're going to have 11 tenths. The 10 tenths from here
plus 1 is 11 tenths. Now let's take one
of those tenths so that we have 10 tenths,
and give it to the hundredths. So that's going to
be 10 hundredths. And now let's take one
of those hundredths-- so now we have nine hundredths--
and give it to the thousandths. So that's going to
be 10 thousandths. Now we're ready to subtract. So 10-- let me do this in
yellow-- 10 minus 4 is 6. 9 minus 9 is 0. 10 minus 7 is 3. We have our decimal point. 8 minus 0 is 8. And then we have 3
minus nothing is 3. So we're done, 38.306.