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## Early math review

### Course: Early math review > Unit 4

Lesson 7: Repeated addition# Adding with arrays

Sal shows how to relate repeated addition to an array. Created by Sal Khan.

## Want to join the conversation?

- Hi I have one question what is a array?(13 votes)
- An array is a way to represent multiplication using rows and columns. Hope that answers your question!(12 votes)

- Why can't they just do 5 times 3 instead of addition?(8 votes)
- We can use multiplication but addition is simpler form of multiplication.(10 votes)

- what is 300 + 900 =(10 votes)
- 900 hundred + 300 hundred is... lets look at this 9 plus 3 and that's 12 s its 1012 because you added 3 to nine and we cant make it 112 because that will be subracting to we have to use addition! Hope this helped :)(3 votes)

- I have one question what is 900+900(7 votes)
- 900 + 900 is 1800 because 9 + 9 = 18 and since it is 900 you have to times it by 100 at the end ( if you are making it simpler) and you get 1800!

Hope this helps!(2 votes)

- how do you change your avatar(6 votes)
- take me out to the ball game take me out to the crowd buy me some peanuts and cracker jacks i dont care if i ever get back root root root for the home team its a shame if they dont win for its 1 2 3 stirkes your at the oldddd ballllll gameeee(5 votes)
- hep me dunno wat is an array(4 votes)
- an array is a array(3 votes)

- are any of you going to anser(5 votes)
- tttttth fuf fuf fuf fuf(5 votes)
- what is an arrey(1 vote)
- Think of an array as a grid with rows and columns. For example if you look at a chessboard, you will see an 8 by 8 array of squares.

Have a blessed, wonderful day!(9 votes)

## Video transcript

- [Narrator] What we're
going to do in this video is think about how many
blocks we have here and instead of just counting them, we're gonna think about it using addition. So how do we do that? Well, we have three rows here, one, two, three rows, and each of these rows
we can see very clearly has one, two, three, four, five blocks. Same thing here in that second row, we have one, two, three,
four, five blocks. Same thing here in this third row, one, two, three, four, five. So one way to think about
the number of blocks we have, is we have
five in this first row, so that would be five, plus
five in the second row, that's another five, plus
five in the third row, plus five just like that. So if you wanna know how many blocks, it would be the same thing
as five plus five plus five. Now I know what some
of y'all are thinking, instead of just thinking
about them in terms of rows, what if we thought about
'em in terms of columns. So here we said we have five
plus five plus five blocks, but we could also think about it as, we have five columns and
each of those columns have three blocks. So that's my first column, this is my second column, this is my third column, this is my fourth column, y'all are getting the picture, this is my fifth column. And each of them have
one, two, three blocks. So this is going to be three plus three from the second column I should say, plus three from the third column, plus three from the fourth column, plus three from the fifth column. So that's interesting,
this number of blocks could also be represented
as three plus three plus three plus three plus three, which we saw is actually the same thing as five plus five plus five.