Understanding the standard algorithm when adding within 1,000
About this video
The narrator checks which worked example correctly adds 647 + 235 using the standard algorithm. Adding the ones gives 12, so 2 is written and 10 ones are regrouped as one ten. The answer is 882, and the choice that shows the regrouping (C) is correct, while B forgot to regroup.
You'll be able to
- add three-digit numbers using the standard algorithm.
- regroup 10 ones as one ten when the ones add to more than 9.
- check someone else's work by doing the problem myself.
Key words
- standard algorithm
- The usual step-by-step way people add numbers, place by place, starting with the ones.
- regroup
- To trade 10 of one place value for 1 of the next place, like 10 ones for 1 ten.
- place value
- The value of a digit based on where it is: ones, tens or hundreds.
Transcript
- [Narrator] We are asked which of the following correctly shows the sum using the standard algorithm? So pause this video, have a go at that before we do this together. Alright. What I always like to do when I'm trying to analyze someone else's work is just try to do it myself.
So if I have 647 plus 235, and when we say standard algorithm, that's just a fancy way of saying... Just the standard way that people normally add three digit numbers like this. So for example, we can start here in the ones place and we have seven ones plus five ones is 12.
Well, 12, we can write that as two ones. And then regroup 10 of those ones right over here. And then we have, let's see, we're going to have one, and actually we can already rule out this one right over here, B because they didn't regroup. They didn't regroup those 10 ones as one 10 right over here.
So we don't see that here, but let's just keep going. So we have one 10 plus four 10's. So one plus four is five, plus three is eight 10's, no need to do any regrouping. And then six hundreds plus two hundreds is eight hundreds, so the answer is 882. So we know that, that checks out there.
And we also had to regroup ones right over there, that 10. And we see that over here. So we like choice C.
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