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Studying for a test? Prepare with these 5 lessons on Module 2: Place value and problem solving with units of measure .

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# Adding 3-digit numbers

Video transcript

Let's add 536 to 398. And we're 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 + 8?" Well, we know that 6 + 8 is equal to 14. And so when we write it down here in the sum, we could say, “ "Well look. The 4 is in the ones place.” So it's equal to 4 + 1 ten." So let's write that 1 ten in the tens place. And now we focus on the tens place. We have 1 ten + 3 tens + 9 tens. So, what's that going to get us? 1 + 3 + 9 is equal to 13. Now we have to remind ourselves that this is 13 tens. Or another way of thinking about it, this is 3 tens and 1 hundred. You might say, "Wait, wait! How does that make sense?" Remember, this is in the tens place. When we're adding 1 ten + 3 tens + 9 tens, we're actually adding 10 + 30 + 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 numbers in the hundreds place. 1 + 5 + 3 is equal to – let's see. 1 + 5 is equal to 6, + 3 is equal to 9. But we have to remind ourselves: this is 9 hundreds. This is in the hundreds place. So this is actually 1 hundred. So this is actually 1 hundred + 5 hundreds + 3 hundreds, is equal to 9 hundreds. And that's exactly what we got here. 100 + 500 + 300 is equal to 900. And we're done. This is equal to 934.