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Intro to place value

Sal introduces place value using a toy with beads (an abacus).  Created by Sal Khan.

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Video transcript

Voiceover:Hey Sal. Voiceover:Hello Brit. Voiceover:I picked this up at a garage sale and I know you like colors. Voiceover:I love colors. Voiceover:You wear colorful shirts everyday and I thought you might like this. Voiceover:I do, this is very kind, I like it. So what are you hoping to do with this thing? Voiceover:Well, at minimum just maybe represent numbers. Voiceover:To count, keep track of numbers? Voiceover:Counting the number of days or... Voiceover:One, two, three, yeah I can imagine doing that. Voiceover:Okay, so moving the beads down is a number, right? Voiceover:Yeah. Voiceover:There's 10. Voiceover:10 there, so maybe that would be 20, 30, 40, 50, 60, 70, 80, 90,100. Yeah, you could count 100 beads to keep track of things. Voiceover:What if I need to count 105 or 106? Do I need to buy another one? I don't even know where I would get more of these. Voiceover:That would be an option, maybe not an option if you don't know where to get it. Let's see, well the different colors, just like we have different forms of currency, maybe we can have each of these colors, maybe the columns, they represent a different amount. So this is 10 right over here, what if we had one of these red beads represent 10 of these blue beads in the first column. So then, you could go, this would be 10 or you could say that is 10. Voiceover:So there's two representations of 10 here? Voiceover:Yeah, they way we just worked it out here, yeah. And then 11 would be that. Voiceover:And this is 21. Voiceover: 21. Voiceover:Yep, you have two 10s and a one, 21. Voiceover:The wooden colored is going to represent all of the red beads. Voiceover:Yeah, that's a good system. If each column represents 10 of the beads to the column to it's right, that could be interesting. Because if this represents 10 red beads, that's 10 10s, this is equivalent to 100 blue beads. And so this would be equivalent to 10 of the brown beads, which would be 100 of the red beads, which would be 1000 of the blue beads, and this would be 10,000 of the blue beads and this would be 100,000 of the other blue beads, this would be 1,000,000 of the blue beads. Voiceover:So we're going to be able tor represent all the numbers in between one and say 1,000,000. Voiceover:I think we can. Voiceover:Let me just give you a number. What about 15,003? Voiceover:So let's think a little bit about this. So let's try with the big numbers first. So each of these is one, each of these is 10, each of these is 100, each of these is 1000. I don't have 15 of these, but these are 10,000. Each of these are 10,000. So this is one 10,000, then I could do five 1000s. One, two, three, four, five, so this is 15,000. So one 10,000, five 1000s, and zero 100s, zero 10s, and then throw a three there. So 15,003.