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## Class 2

### Course: Class 2 > Unit 3

Lesson 1: Adding with regrouping# Adding 53+17 by making a group of 10

Sal adds 53+17 by breaking apart the numbers and making a group of 10.

## Want to join the conversation?

- Can you show me a different way please?(12 votes)
- Another way is separating the tens from the ones in both numbers:(50+3) + (10+7)

Then reorganizing so the tens are together and the ones are together: (50+10) + (3+7)

And you get: (60)+(10)

Which adds up to become: 53+17=70(22 votes)

- How can this be equal to 53+17=70? Why?(5 votes)
- Well because if you were to break it down, into this 50 + 10 and 3 + 7

First, solve for 50 + 10, it equals 60

And 3 + 7 = 10

So 60 + 10 = 70

You get it?(17 votes)

- I have a problem that is 47+23

= 47 (*__*)+20

= (47 +*__*)+20

=*__*+ 20

=*__*

I've been working on this problem for an hour now and I still cant seem to figure out the problem somebody please explain this to me the video is not helpful thanks.(6 votes)- you just had to separate the 3 from the 20

= 47 (**3**)+20

= (47 +**3**)+20

=**50**+ 20

=**70**

Hope this helps.(8 votes)

- How do you figure out 53+17?(3 votes)
- 53+17

=50+3+17

=50+20

=70(5 votes)

- Why do you have to carry the one? Couldn't you just put it right next to the zero?(3 votes)
- No, you cannot just leave the answer as 610, because that would be 6
**hundreds**and 10 ones. Note that 53+17 is 6**tens**and 10 ones.

Have a blessed, wonderful day!(3 votes)

- 45 + 67 can be answered by lining up the numbers like so (please ignore the hyphens, they are for formatting purposes) :

-- 45

+ 67

=

First, add the two left most numbers, those being 5 an 7. The result of this is 12, so place a 2 in the "ones" section of the answer and a 1 above the "tens" section of the question like so:

--**1**

-- 45

+ 67

- =**2**

Next, add all the numbers on the left most part of the equations togethers, including the one on the top. This would be 1 + 4 + 6, resulting in 11. This can be placed directly in the answer place, considering that there are no more numbers to the left.

-- 1

-- 45

+ 67

=**117**

And thus, we have our answer,**117**. I hope this helps :D(1 vote)

- Why do you have to carry the one? Couldn't you just put it right next to the zero?(0 votes)
- Gracie , if you didn't carry over the one it would go to the thousandths place which is not correct (even by estimating). Hope this helped !(3 votes)

## Video transcript

- What I want to calculate in this video is 53 plus 17, plus 17. And the way that I want to do it is by breaking up the 53 and
then rearranging the numbers, and you'll see what I'm
talking about in a second. So 53 plus 17, that's going
to be the same thing as, I'm gonna break up 53, essentially into the tens and the ones. So 53 can be rewritten as 50 plus 3. That's 53 right? And I could put parentheses
around it like this. So these curvy things, so
this is an open parenthesis and this is a close parenthesis. This just means to do whats
inside the parentheses first. So 53 is the same thing as 50 plus 3 and we still have the plus,
we still have the plus 17. Now, I could just add the 50 plus 3 first and then add the 17 and that would just get back there, but we want to figure out what this whole thing is. So I could rewrite this,
this is the same thing as 50 plus 3 plus 17, plus 17, and I could do the 3 plus 17 first. So here I'm doing the 50 plus 3 first, I have those in the parentheses. Here I'm doing the 3 plus
17 first, and this is just a property of addition
that I could do this. I could change the order
in which I'm adding. So here I'm adding 50 plus 3 first. Here I'm going to add 3 plus 17 first. And so what's this going to be equal to? Well this is going to be equal to I have my 50 here, I have my 50 plus, now whats 3 plus 17? What's 3 plus 17? Well 3 plus 7 would be 10, so
3 plus 17 is going to be 20. So it's going to be 50 plus 20. Now what's that going to be? Well it's 5 tens plus 2 tens,
which is going to be equal to this is just going to be
equal to 7 tens, or 70. Let's do another example,
and this is going to be one like the type of exercise that you might see on Khan Academy. So let's, let me take, open that up. So they'll say "Complete
to solve 41 plus 9" so once again we can look at, we can look at the 41
and we can break it up. 41 is the same thing as 40 plus what? Well, it's 40 plus 1, and of course then you have the plus 9
there and I can do the 9 see this plus 9 is this plus 9 there. Now they change the order
in which we're adding. So 40 plus 1, that's in the parentheses and then you add 9, well that's
the same thing as 40 plus well, that's the same
thing as 40 plus 1 plus 9. So here we're doing the 1 plus 9 first, and if we do the 1 plus
9 first what do we get? Well, 1 plus 9, 1 plus 9 is what? Well, that's just going to be equal to 10. Notice what this, this box is replacing what was in the parentheses before, so in the parentheses you
had 1 plus 9, well that's 10. And what's 40 plus 10? Well it's 4 tens plus
1 ten so that's 5 tens. Or, 50, and we're done.