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## Numbers & Operations - The Real & Complex Number Systems 159-175

### Course: Numbers & Operations - The Real & Complex Number Systems 159-175>Unit 2

Lesson 2: Intro to addition with 2-digit numbers

# Adding within 20 using ten frames

Sal adds 8 + 7 using ten frames. Created by Sal Khan.

## Video transcript

- [Instructor] In this video, we want to figure out what is equal to eight plus seven. And I'm gonna give you a little bit of help by drawing what is known as ten frames. And these are useful because as you can see, each of these frames have ten boxes in them. One, two, three, four, five, six, seven, eight, nine, 10. Or you could see that it has five and then another five, so a total of 10. So we can represent each of these numbers in their own ten frame, so we could view this as eight, so we can fill in eight of these squares. One, two, three, four, five, six, seven, eight. And that's going to be eight plus seven. So let's fill in seven of those squares. One, two, three, four, five, six, and seven. So using this all as a hint, what is equivalent to eight plus seven? Pause this video and try to think about it. All right, now let's do this together. So the reason why ten frames are useful is you can think about how many would you have, how many of these circles would you have to move from this ten frame into this ten frame on the left in order to fill it up, and order to have 10 right over here? And you can see that we have two spaces to fill up. So what if we were to remove two of these yellow circles into this left ten frame? What would then happen? So I'm going to erase this one and this one, and remember that I didn't lose them. I just have to put them in a different place now. I'm going to put those two right over here. So one and two. So notice, I still have the same number of circles. I still have those seven yellow circles. One, two, three, four, five, six, seven. But I just wrote it a little differently so that two of them fill up the left ten frame. Now this helps us think about what this sum is going to be, why is that? Because now we filled out all the squares in this left ten frame. So we know that this left side right over here, this is going to be 10, and now what's left in this right side? Well, this right side, you can see we filled out half of the ten frame. Or one, two, three, four, five squares. So eight plus seven is same thing as 10 plus five, which you might recognize is going to be equal to 15. And you can obviously verify that by counting all these. We have 10 here, and then 11, 12, 13, 14, 15.