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## Arithmetic (all content)

### Unit 2: Lesson 9

Strategies for adding and subtracting within 100- Adding 53+17 by making a group of 10
- Add 2-digit numbers by making tens
- Adding by making a group of 10
- Add 2-digit numbers by making tens 2
- Strategies for adding 2-digit numbers
- Select strategies for adding within 100
- Addition and subtraction with number lines
- Add within 100 using a number line
- Subtract within 100 using a number line

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# 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 u show me a different way please.(10 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(15 votes)

- Why do they make it so much harder than it actually is.(10 votes)
- I agree with you on that, I think that Sal explaining it too much. :)(3 votes)

- I'm confused by all of the math, is there another way to make it a lot easier(9 votes)
- Maybe just add the digits vertically, This is what works for me.

You can also use colours too.(or do something in a difference)

Ex.**53**+17

=**50**+(**3**)+17

=**50**+20

=70(2 votes)

- How can this be equal to 53+17=70? Why?(1 vote)
- 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?(10 votes)

- in my class, we have a rule about Pemdas p stands for parentscy and e stands for exponent(3 votes)
- PEMDAS stands for parenthesis, exponents, multiplication, division, addition, and subtraction. It is Pemdas to help you remember it.(2 votes)

- i did not understand that(3 votes)
- You first add 3 and 7 together.

Next, you carry 1 from the 10 and leave the 0 be to the tens.

Lastly, add the carried 1, 5 and 1 together to get 7.

Answer is 70.(0 votes)

- you make it harder than it shoud be(3 votes)
- Some people think differently about math than you do. Some kids need to have the 7 & the 3 removed from their numbers then added together to understand adding 2-digit numbers.(1 vote)

- that video to counting decmal numbers such as 17,5 + 18,9 ?(1 vote)
- I watched the video but what is 53+18(1 vote)
- 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.(1 vote)- you just had to separate the 3 from the 20

= 47 (**3**)+20

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

=**50**+ 20

=**70**

Hope this helps.(4 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.