Lesson Video: Column Addition of Three-Digit Numbers: Regroup Tens Mathematics • 2nd Grade

In this video, we will learn how to add two three-digit numbers when we have to regroup tens and record the calculation in columns.

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Video Transcript

Column Addition of Three-Digit numbers: Regroup Tens

In this video, we will learn how to add three-digit numbers when we have to regroup tens and record the calculation using column addition.

When we’re adding three-digit numbers using column addition, we need to use our knowledge of place value. Three-digit numbers have a hundreds digit, a tens digit, and a ones digit. We start adding in the ones column. Then, we have the tens in the tens column. Then, we add in the hundreds column. Do you know why we always start adding in the ones column? We do this in case we need to regroup. The greatest number of ones we can have in the ones column is nine. When we have 10 ones, we have to regroup. We have to exchange our 10 ones for one 10. The greatest number of tens we can have in the tens column is also nine. When we have 10 tens, we have to regroup. We exchange our 10 tens for 100. In this video, we’re going to be learning how to regroup in the tens column.

In this example, we have to use column addition to add together 271 and 354. We’ve modeled our calculation using a place value chart and some place value blocks. We always start adding in the ones column. We need to add together one and four, which gives us a total of five ones. Now, we need to add the tens. 271 has seven tens, and 354 has five tens. So, we need to add together seven tens and five tens. Seven and five is 12. But this is not how we write it. Once we have 10 tens, we need to regroup. And we know that 12 is more than 10. We need to regroup 10 of our tens and exchange them for 100.

Now, we can write the remaining two tens. We need to exchange our 10 tens for 100 and write a one in the hundreds column because 10 tens equal 100. We had 12 tens. Now, we have two. We exchanged 10 tens for 100. Now, when we’re adding in the hundreds column, we can add our two hundreds and three hundreds, which gives us a total of five. And then, we need to add the one we exchanged. Five and one more is six. So, 271 plus 354 is 625. We had a total of 12 tens. We regrouped and exchanged 10 of our tens for 100.

Let’s practice adding three-digit numbers where we have to regroup the tens using some questions.

Use place value blocks to show how to add 342 and 183.

In this question, we have to use column addition to add together 342 and 183. And the question tells us to use place value blocks to help. When we use column addition to add together two three-digit numbers, we always start adding in the ones column, 342 has two ones and 183 has three ones. So, we need to add together two and three. Two ones and three ones gives us a total of five ones. We need to make sure to write the five in the correct column; we need to write it in the ones column. 342 has four tens and 183 has eight tens. So, we need to add together four tens and eight tens. Four and eight is 12. We need to regroup some of our tens. 10 tens make 100. So, we can exchange 10 tens for 100.

Now we have two tens, which we can write in the tens place. And we need to add 100 into the hundreds column because we exchanged 10 tens for 100. And we need to remember to add this 100 when we’re adding in the hundreds column. 342 has three hundreds; 183 has 100. We know that three plus one is four. Now, we just need to add the 100 we exchanged. Four plus one gives us a total of five hundreds. 342 plus 183 is 525.

We used column addition to add together 342 and 183 to give us our total of 525. We used the place value blocks to help.

Find the sum. 275 plus 331.

In this question, we’re asked to find the sum of 275 and 331. Sum is another way of saying total. This is the total we get when we add together two or more numbers. We can see from the way the question’s been set out that we need to use column addition. Let’s start by adding in the ones column. We need to add together five and one; five and one is six. Next, we need to add the tens. We’ve got seven tens and three tens. Seven plus three is 10. 10 tens are 100. So, we can write one in the hundreds column because we’re exchanging 10 tens for 100. And we need to write a zero in the tens column. 10 tens are 100. So, we have 100 and no tens. Now, we just need to add the hundreds. Two plus three is five plus the one we exchanged is six. The sum of 275 and 331 is 606.

First, we added in the ones column, then the tens column. There were 10 tens. We exchanged these 10 tens for 100, and then we added the hundreds column. 275 plus 331 is 606.

Find the following: 376 plus 243.

In this question, we’re being asked to use column addition to help add together two three-digit numbers, 376 plus 243. It helps to set our calculation out on squared paper. We can use the squares to help us make sure we write each digit in the correct column. First, we add the ones; we’ve got six and three. Six ones and three ones gives us a total of nine ones. Next, we need to add the tens. 376 has seven tens, 243 has four tens. So, we need to add together seven and four. Seven and four makes 11. We can write one in the tens place, and we need to exchange the other 10 tens for 100.

Finally, we need to add the hundreds. Three plus two is five plus the one we exchanged gives us a total of six. Nine ones, 11 tens, we exchanged 10 tens for 100, we had five hundreds, then we had to add the one we’d exchanged to give us a total of six hundreds. 376 plus 243 gives us a total of 619.

We added together our two three-digit numbers, starting in the ones column. Next, we added the tens column. Because we had 11 tens, we had to regroup. We exchanged 10 tens for 100. And finally, we added the hundreds. 376 plus 243 is 619.

What have we learned in this video? We’ve learned how to add three-digit numbers using column addition. We’ve also learned how to regroup the tens. And we’ve learned that we can exchange 10 tens for 100.

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