Adding decimals and whole numbers (thousandths)
At about 88-92s the narrator says 'one 10 plus another 10 that is two-tenths' when he means two tens (the answer is 21.628). At about 152s he also says 'zero hundreds' when he means zero hundredths. The interventions use the correct terms.
The check-ins use the correct version. The video is Khan Academy's, unchanged.About this video
This video shows how to add a whole number to a decimal with thousandths, such as 7 + 14.628 and 6 + 0.739. It uses two methods: splitting the decimal into its whole part and decimal part to add in your head, and lining the numbers up by place value with zeros as placeholders.
You'll be able to
- add a whole number to a decimal with thousandths.
- line up numbers by place value, keeping the ones places and decimal points lined up.
- write a whole number with zeros after the decimal point, like 6 = 6.000, to help me add.
Key words
- place value
- The value a digit has because of where it sits in a number, such as ones, tens, tenths or thousandths.
- thousandths
- The third place after the decimal point; one thousandth is 1/1000 or 0.001.
- regroup
- To trade 10 of one place value for 1 of the next bigger place, like 11 ones becoming 1 ten and 1 one.
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.
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