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00:00Right here right now we are going to learn something exciting called double
00:05digit addition. You may have already seen our basic addition video. In that video
00:12we learned that addition means putting numbers together. We learned about this
00:16lady named Sally who collects golf balls. Let's say Sally starts her day off with
00:24two golf balls. Cool! And then she finds another golf ball. So now we get to find
00:31out how many she has in total. She had two and now she's got another one. How
00:37many golf balls does she have? This is addition. Two plus one. Can you add those
00:45up? What's two plus one? Uh-huh. Three. Awesome. Let's look at one more example
00:55of basic addition before we get into the double digit addition. Let's say later on
01:02in the day Sally has five golf balls and then she finds two more that are just
01:09sitting there. Just sitting there. So she can add the two golf balls to the five
01:14that she already has. Remember addition is putting numbers together. Five plus
01:21two equals what? Here's a hint. You can count these golf balls up and get the
01:27answer. Yeah. Seven. Five plus two equals seven. You are doing a tremendous job.
01:39These are examples of single digit addition. But what if we need to add
01:46bigger numbers? Let's say there's this kid named Travis. Hi Travis. Travis
01:57collects these. What are these called? Uh-huh. Marbles. Travis collects marbles.
02:08Travis had a lot of marbles. He had 54 marbles. But today's his birthday and
02:14someone just gave him 21 more marbles. Wow. And now he wants to know how many
02:21marbles do I have? I had 54 and now I have 21 more that are in my collection.
02:29How many marbles do I have? That's the question that Travis has. What's 54 plus
02:3721? Now here's the deal Travis. You could count each of the marbles one by one to
02:47figure out exactly how many you have now. But that would take a long time. Look at
02:55all of these marbles. There has to be a better way. In fact there is. There's a
03:01way that is super fast and super fun. We can add 54 and 21 together by doing a
03:11fun trick. We'll turn these big numbers that are difficult to add on their own
03:15into smaller numbers. What you will do is you will add the numbers to the right
03:20right here which are the ones. To make it easier we are going to block the 10
03:25spot for right now with this nifty blue rectangle. Suddenly this huge big addition
03:32problem has turned into a simple fun addition game. So we add the right spot
03:36the one spot together. What is 4 plus 1? Yes 4 plus 1 equals 5. So we'll write 5
03:47under the 4 and the 1. Awesome job! We're halfway done already. Next we will
03:55add the 10s together. The 10 spot is to the left. The two numbers in the 10 spot
04:01are the 5 and 2. To make it easier we are going to block the one spot with
04:07another blue rectangle because we already added the one spot up. What is
04:125 plus 2? Uh-huh 5 plus 2 equals 7. So we will write 7 under the 5 and the 2. So
04:27what is our answer? What is 54 plus 21? Uh-huh you can see it right here 75. 54
04:35plus 21 equals 75. The answer to an addition problem is called the sum. Our
04:46sum is 75. It's simple with double digit addition you add the right side the ones
04:56together first. Let's figure out what 30 plus 12 is. First what is 0 plus 2?
05:04Yes 0 plus 2 is 2. So we'll write a 2 under the right side the ones side. We've
05:13almost arrived at our answer already. Then we add the left side the 10s to get
05:20our answer. What is 1 plus 3? Yep 1 plus 3 equals 4. So the sum of this addition
05:33problem is 42. 30 plus 12 equals 42. Let's try a different type of addition
05:45problem 33 plus 6. This is an interesting one because 33 is a double
05:51digit number but the number 6 is a single digit number but we use the same
05:57fun trick as before. First we add up the ones. What is 3 plus 6? Uh-huh 3 plus 6
06:09equals 9. So we write 9 here under the ones. Next let's add up the 10s but there
06:20is only one number in the 10 spot. So what do you get if you add nothing to
06:253? Uh-huh you get 3. So what is our sum? Yes our sum is 39. How are we doing?
06:42Double digit addition is pretty cool isn't it? Now we are going to talk about
06:46something special, really special. Special like seeing an Owlette, a little baby
06:54owl looking at you, looking at your eyes. So cute, so special. So what is this
07:04special thing we are about to learn? Well sometimes something sneaky happens. Let's
07:11show you. Let's say we are adding 17 plus 15. We of course start with the right
07:20side adding up the ones first. So what is 7 plus 5? Do you know? 7 plus 5. Yeah 7
07:30plus 5 equals 12. That's right but there's only enough room for one digit
07:36under the 7 and the 5. So what do you do? Well we do a super cool move called
07:45regrouping. Regrouping. Regrouping is awesome. Remember the sum of our ones
07:55column is 12. 7 plus 5 equals 12. So we have to regroup the number 12 but what
08:01does that mean? What does regrouping even do? Well regrouping splits the digits
08:09and puts them in different places. Now that might sound weird but we're gonna
08:14show you how it works. It's super simple and fun.
08:21Regrouping the number 12 is easy. All we do is split the digits putting the 2
08:26under the ones and carrying the 1 with the tens up here. That's it. Then we add
08:36up the tens. What is 1 plus 1 plus 1? Yeah 1 plus 1 plus 1 equals 3. So we
08:46write 3 under the tens and now we have our answer. 17 plus 15 equals 32. 32 is
08:56our sum.
09:00Remember regrouping is only used when there is a double-digit number but
09:08there's only space for one digit. Like our example 7 plus 5 equals 12 but there
09:14wasn't enough room for both numbers. So we keep the 2 under the ones and carry
09:19the 1 to the tens. Hey let's practice by playing a game. The game is called do we
09:28need to regroup? This is probably the most exciting double-digit addition game
09:36ever. Hosted by our very own Mr. Whiskers. Thanks for helping us out.
09:46You're not you're not gonna help us out. Okay. Okay now now this is embarrassing.
09:53Okay. Fine. Okay. All right. That's okay. All right. Well we are going to look at
10:06double-digit addition problems and you are gonna let us know. Do we need to
10:12regroup? Here is our first problem. 32 plus 19. You already know the question.
10:21When we add 32 and 19 do we need to regroup?
10:34Yes because 2 plus 9 equals 11 which is a double-digit number. Remember the first
10:41step we take is adding up the ones but if the sum is a double-digit number that
10:47means we need to regroup. Great job.
10:54Let's go ahead and finish the problem. When we regroup we split the digits so
11:01the first one gets carried and the second number in this case also the
11:06number one stays down under the ones. Then we just add up the tens. What is 1
11:12plus 3 plus 1? Uh-huh. 5. So 32 plus 19 equals 51 and yes we did have to regroup.
11:28Here is our second one. 56 plus 22. This is the question. When we add 56 and 22 do
11:38we need to regroup? No because 6 plus 2 equals 8 and 8 is a single-digit number
11:53that can fit under the ones. Remember the first step we take is adding up the ones
11:59and since the sum is a single-digit number already we do not need to regroup.
12:05Fantastic. Let's go ahead and finish the problem. So when we added up the ones our
12:13sum was 8. We'll put the 8 under the ones. Then we just add up the tens. What
12:19is 5 plus 2? Uh-huh. 7 and we have our answer 56 plus 22 equals 78 and no we
12:31did not have to regroup. Here is our next one. 34 plus 25. This is the
12:43question. When we add 34 and 25 do we need to regroup?
12:51No because 4 plus 5 equals 9 and 9 is a single-digit number that can fit under
13:05the ones. Remember the first step we take is adding up the ones and since the sum
13:10is a single-digit number already we do not need to regroup. Well done. Let's go
13:19ahead and finish the problem just for fun. So when we added up the ones our
13:24sum was 9. We'll put the 9 under the ones. Then we just add up the tens. What
13:30is 3 plus 2? Uh-huh. 5 and we have our answer 34 plus 25 equals 59 and no we
13:42did not have to regroup. This is our last one. You have been doing great. 43
13:55plus 37. You already know the question. When we add 43 and 37 do we need to
14:02regroup? Yes because 3 plus 7 equals 10 which is a double-digit number. Remember
14:15the first step we take is adding up the ones but if the sum is a double-digit
14:20number that means we need to regroup. Wonderful. Let's go ahead and finish the
14:31problem. When we regroup we split the digits so the number 1 gets carried and
14:36the second number in this case the number 0 stays down under the ones. Then
14:41we just add up the tens. What is 1 plus 4 plus 3? Uh-huh. 8. So 43 plus 37 equals
14:5480 and yes we did have to regroup. We've had such a great time. In this video we
15:03have learned so much about double-digit addition. Two of the biggest things we
15:08learned is how it works. We add the ones first, the right side, and then add the
15:14tens, the left side. We also learned about something special called regrouping
15:20and how we need to regroup the sum of a column if it is a double-digit number.