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### Course: 1st grade > Unit 2

Lesson 2: Addition within 20# Adding 8 + 7

In the video it demonstrates adding 8 + 7 using a visual approach. Adding emphasizes the concept of place value, showing that 15 is made up of 1 group of 10 and 5 ones. This method helps students understand addition within 20 in a more concrete way. Created by Sal Khan.

## Want to join the conversation?

- What is the importance of Adding?(19 votes)
- Math is a way to analyze complex problems and the world around you. It helps your brain connect pathways and come to quicker solutions by breaking down a problem to its most basic ingredients (first principle thinking). It's only when you're able to break down a problem to its most fundamental components, you're able to see the solution. In math, we do this by using an abstract language (numbers)

Example:

8 + 7

10-8=2

7-2=5

10+5=15(16 votes)

- What does represent mean??(2 votes)
- Represent means what something means. For example, a drawing of something you saw
what you saw, even though you aren't there anymore. In math, we can represent the numbers with the amount of fruits, or the other way around, representing the amount of fruits with numbers. For example, 2 oranges = 🍊🍊 and 🍊🍊 = 2 oranges. Also, like said in the video, one number can represent more numbers. 15 can mean 10 + 5, since the 0 is basically nothing, yet it is important because it makes the 1 before it 10 times bigger.**represents**(2 votes)

- My teacher teached me this poem more on top? no need to stop! More on the floor? Go next door and get ten more! Numbers the same zeros the game!

That was a subtraction poem and I think it was a good rhyme and also number lines are used for counting like 8 minus 3 start at 8 and go down three

7 6 5 so the answer is five come to me for help(0 votes) - why are number lines important?(0 votes)
- Number lines are important because one day you may need them to put fractions on,add on,subtract,multiply on,and dived you may need it through out your life time.. if you didn't need it they wouldn't teach it,..(0 votes)

## Video transcript

Voiceover:Let's try to think about what 8 plus 7 is equal to. And we could imagine that this is like taking 8 tomatoes and adding 7 blueberries and then saying, "How many pieces of fruit "do you have in total?" I encourage you to pause the video and try this out on your own. So, I'm assuming you've given a try. So let's think about it a little bit. And the way I'm going
to think about it is, I'm going to keep adding
tomatoes until I fill up my first bucket of 10
and then I'm going to see how many more I have to add to get, to essentially, add a total of 7. So let's have 1 tomato,
2 tomatoes, 3 tomatoes, 4 tomatoes, 5 tomatoes, 6 tomatoes, 7, and 8 tomatoes. Now, to those 8 tomatoes I'm going to add 7 blueberries. So that's going to be 1, 2 ... And actually, I'm going to pause there. Because I just finished a group of 10. This, right over here, I've only added 2 of the blueberries. I still have some more blueberries to add, but just with adding those 2 blueberries, I have completed a group of 10. So I already have 10 pieces of fruit. So I can represent that. I know, since I have a group of 10 here, that I have 1 group of 10. So this is going to be a 2 digit number, where the digit on the
left is going to be a 1. But I'm not done adding blueberries. I've only added 2 blueberries. Now let me add a third. 3 blueberries, 4
blueberries, 5 blueberries, 6 blueberries, and 7 blue berries. So I have a group of 10 and then, above and beyond filling
out that group of 10, which is represented here,
because this is going to be a 2 digit number. This is the left digit. So this 1, since it's in
the tens place, it literally represents 1 group of 10,
which is right over there. And then how many more do I have? Well I have another ... I have another 5, 1's. 5, 1's right over here. So we have 1, 10 and we have 5, 1's. So what is 8 plus 7? It is 15. And another way, just to remind ourselves what 15 represents. The 1 in 15 represents 1, 10. Let me write it down. It represents, it represents 1, 10. And the 5 represents 5, 1's. 5, 1's. And so another way of thinking about it, 1, 10 is the same thing as 10 and 5, 1's is the same thing as 5. So 8 plus 7 is 15. That was the whole point of this video. But we also want to think about what these numbers represent. 15 literally represents 1, 10 plus 5, 1's. Or 10 plus 5.