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## 3rd grade

### Unit 3: Lesson 4

Adding with regrouping within 1000# Using place value to add 3-digit numbers: part 1

Learn to use regrouping, or carrying to add 536+398. Created by Sal Khan.

## Video transcript

Let's add 536 to 398. I'm going to do it two
different ways so that we really understand what this
carrying is all about. So first we'll do it in
the more traditional way. We start in the ones place. We say, well, what's 6 plus 8? Well, we know that 6
plus 8 is equal to 14. And so when we write it down
here in the sum, we could say, well, look, the four is in the
ones place, so it's equal to 4 plus one 10 So let's write
that one 10 in the tens place. And now we focus
on the tens place. We have 1 ten, plus
3 tens, plus 9 tens. So what's that going to get us? 1 plus 3 plus 9 is equal to 13. Now, we have to remind
ourselves, this is 13 tens. This is 13 tens. Or another way of thinking
about it, this is 3 tens. This is 3 tens and 100. You might say, wait, wait. How does that make sense? Remember, this is
in the tens place. When we're adding a 1 ten
plus the 3 tens plus 9 tens, we're actually adding 10 plus 30
plus 90, and we're getting 130. And so we're putting the 30. The 3 in the tens place
represents the 30. So this is the 3. The 3 represents the 30. And then we're placing this
1 in the hundreds place. 10 tens is equal to 100. And now we're adding
up the hundreds place. 1 plus 5 plus 3 is
equal to-- let's see, 1 plus 5 is equal to 6,
plus 3 is equal to 9. But we have to remind
ourselves, this is 900. This is in the hundreds place. So this is actually 100-- I want
to make all colors the same. So this is actually
100 plus 500 plus 300. Let me get the
color coding right. Plus 300 is equal to 900. And that's exactly
what we got here. 100 plus 500 plus 300 is
equal to 900, and we're done. This is equal to 934.