Sal shows how to relate repeated addition to an array. Created by Sal Khan.
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- What is an array?(7 votes)
- 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.
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- Why can't they just do 5 times 3 instead of addition?(17 votes)
- How would we sort 25 into an array?(8 votes)
- [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.