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### Course: Get ready for 3rd grade > Unit 1

Lesson 3: Add within 100- Adding 2-digit numbers without regrouping
- Adding with regrouping
- Add within 100 using place value blocks
- Adding 53+17 by making a group of 10
- Add 2-digit numbers by making tens
- Addition and subtraction with number lines
- Add within 100 using a number line
- Strategies for adding 2-digit numbers
- Select strategies for adding within 100

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# Adding 2-digit numbers without regrouping

Sal adds 23 + 45 thinking about place value.

## Want to join the conversation?

- What if you group the numbers before addition(25 votes)
- It would be the same concept except backwards, you would still get the same answers. 800+50+3=853 358=300+50+8(9 votes)

- Is there a thousands cube and a millions cube?(2 votes)
- Yes, the thousandths cube is a cube with 10 100's, but I have never seen a millions cube. I think they should make those!! :)(1 vote)

- Is there a maximum amount of numbers you can put in an addition or subtraction problem like this?(0 votes)
- Yes, it is infinite. You can have 0 + 0 + 0 + 0 and keep going forever. But if you don't count zeros, I would say there are a maximum 9. That is 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1. Or that could also include 11 + 11 + 11 + 11 + 11 + 11 + 11 + 11 + 11. But if you want different single digits in one equation you can have a maximum of 3 without regrouping. That is 1 + 2 + 3 or 1 + 2 + 4 or 1 + 3 + 4. There are many possibilities.(7 votes)

- its the same as adding 1 + 4 = 3 but how does this help me?(1 vote)
- Can you regroup any number?(0 votes)
- You can regroup any number greater than 10. For example: 84 is 8 tens and 4 ones.(0 votes)

- Would adding fractions or decimals be different?(0 votes)
- Adding doesn't really differ with decimals, but with fractions you sometimes need to expand them first so they have the same denominator. Also when adding fractions, denominators never get added.(0 votes)

## Video transcript

So above this dotted line, I have a certain number of boxes. And we could see each of these gold bars, they have 10 boxes in them. 1, 2, 3... 4, 5, 6, 7, 8, 9, 10 And I have two groups of these tens. So I have two tens. I have two tens and I have 1, 2, 3 ones. That's how many boxes I have above that line and below that line... I have 1, 2, 3, 4 tens. Four tens. And I have 1,2,3,4,5... I have five ones. So, this first number is two tens and three ones or 23. Two tens, three ones. The second number is four tens and five ones. Four tens and five ones...45, now, what I want to do is add the numbers. So let's do that. So let's add, so let's add that amount. This amount to this amount. 23 to 45. Well, I have three ones here, I have five ones here, so if you add those to those you're going to end up with eight ones. So let me do that in that blue color. So you're gonna have: 1, 2, 3, 4, ... 5, 6, 7, 8 and if we look at it... look at it over here where we write down the numbers with digits, or with numerals. Then here you're gonna have three ones plus five ones is eight ones. Eight ones... eight ones. Now you have two tens plus four tens. Well, that's going to be six tens. So let me actually copy and paste this. So I have two tens. So two plus four is six. So two, four and... two, four and six. So I have... I have. Let me change my tools. So I have 1, 2, 3, 4, 5, 6 tens Woops, using the wrong thing. I have... I have six tens. So just like that, you can see when I had 23 to 45, I just added the ones place. Three plus five was eight. Three plus five is eight. Three ones plus five ones is eight ones. And I added the tens place. Two tens plus four tens is equal to 6 tens. So I got 68.