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Course: Grade 5 (TX TEKS) > Unit 5
Lesson 4: Adding decimals (thousandths)Adding decimals and whole numbers (thousandths)
Practice adding decimals and whole numbers together using a variety of strategies. First, practice breaking apart the numbers into whole numbers and decimals. Then, line the decimals up by place to add. Created by Sal Khan.
Video transcript
- [Host] So let's say
we want to figure out what seven plus 14.628 is
equal to, pause this video and see if you can work
through this on your own before we do it together. All right, now, some of you might be able to just do this in your head. You could, for example, view this as seven plus 14 plus 0.628 'cause that's what this
number is right over here, it's 14 plus this. And then you can say, all right,
well that's seven plus 14, which is 21 plus all of this, which would be 21.628. Another way that you could
approach this is you could line them up by place value. So it's seven plus and you just have to make
sure this is the one's place. So we have to line that up
with the one's place over here, plus 14.628. Normally we'd write the number
that has higher place values, higher, but this works as well. And here you would just say, all right, well let's just add up
all of the place values. And I'm putting some zeros here 'cause we have no tenths, no hundredths, no thousandths, but we can still add. So if you add that we
have eight thousandths, two hundredths, six tenths, and then we get to the ones
place, seven plus four is 11 ones, which we could write
down as one one and one 10. And then we've regrouped that. So we have one 10 plus
another 10 that is two-tenths. And so that is what we got. Now let's give another example. And some of you might find this one to be a little bit more straightforward, but it never hurts to get more practice. What if I were to walk
up to you on the street and say, what is six plus 0.739? Pause the video and
try to figure that out. Well, some of you might be
able to figure it out based on what we already did over here. There's many ways you
could think about it. You could say, look, we're
just gonna add six ones to what we already have here. So those six ones are going
to be added right over there. So that would be 6.739, or you could line everything up. You could say this is
gonna be six plus 0.739. Once again, I made sure that
the one's place is lined up with the one's place,
the decimal is lined up, and six is of course
the same thing as 6.000. And then when you add, we have zero plus nine
is nine, thousandths, zero hundreds plus three
hundredths is three hundredths. Zero tenths plus seven
tenths is seven tenths, and then six ones plus
zero ones is six ones. So either way, but hopefully
now you have some practice dealing with decimals and also
adding them to whole numbers.