About this video
Using blocks, the video shows 23 as two tens and three ones and 45 as four tens and five ones. To add them, add the ones (3 + 5 = 8 ones) and the tens (2 + 4 = 6 tens) to get 68.
You'll be able to
- show a 2-digit number as tens and ones.
- add two 2-digit numbers by adding ones to ones and tens to tens.
- explain why 23 + 45 = 68.
Key words
- tens
- Groups of 10 things, shown as long bars.
- ones
- Single things that are not in a group of ten.
- ones place
- The right digit of a number, showing how many ones.
- tens place
- The digit just left of the ones place, showing how many tens.
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.
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