Current time:0:00Total duration:3:04

0 energy points

Studying for a test? Prepare with these 8 lessons on Addition and subtraction.

See 8 lessons

# Adding 3-digit numbers with regrouping

Video transcript

We have three different addition problems right over here. And what I want you to do so you get the hang of things is to pause the video and try them on your own. But as you do them, I want you to really keep in mind and think about what the carrying actually means. So I assume you've tried on your own. Now I'll work through them with you. So we have 9 + 6. 9 ones + 6 ones. Well 9 + 6 is 15. Well, we could write the 5 in the ones place, and then we carry the 1. But what did we just do? What does this 1 represent? Well, we put it in the tens place. 1 ten represents 10. So all we said is that 9 + 6 is equal to 10 + 5, is equal to 1 ten + 5, which is equal to 15. Now, in the tens place, we have 1 + 0 + 9, which is 10. And so we can write 0 and carry the 1. 1 + 0 + 9 is 10. Now what does that really mean? Well this is 1 ten + 0 tens + 9 tens, which is 10 tens. 10 tens is 100. Or another way of thinking about 100, it's 1 hundred, and 0 tens. So that's all that carrying represents. So now we have 1 + 7 + 9. That is going to be 17. Now, we have to remind ourselves, this is in the hundreds place. So this is actually 1 hundred, plus 7 hundreds, plus 9 hundreds, or 17 hundreds. Or 1 thousand, 7 hundreds. And of course we have this 5 here. And we are done. Now let's try to tackle this one. Now the reason why I wrote it that way is to make sure that we remind ourselves to align the proper places under the appropriate places. So this problem we could rewrite as 373 + 88 (stacked vertically). We want to write the ones under the ones place, and the tens under the tens place, so that we're adding the appropriate place values. So 3 + 8 is 11. The 1 in the ones place, and the 1 in the tens place. 10 + 1 is 11. 1 + 7 is 8. 8 + 8 is 16. But this is actually 16 tens. So let me just write down the 16. What is 16 tens? Well, that's 160. So this 6 is a sixty. And then I have 100. 1 + 3 is 4. But these are actually hundreds, so it's 4 hundreds. So we get 461. Now finally, 9 + 3 is 12. 2 ones, and 1 ten. 12 is the same thing as 10 + 2. Now in the tens place: 1 + 4 + 9 is 14. So we write the 4, and carry the 1. But remind ourselves, this is actually 10 + 40 + 90, which is 140. Which is the same thing as 40 + 100. And then 1 + 1 + 2 is 4. But this is the hundreds place. So this is actually 1 hundred, plus 1 hundred, plus 2 hundreds or 4 hundreds. And we're done.