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Use place value blocks to show numbers within 1,000

Sal uses place value blocks to represent numbers within 1000. Created by Sal Khan.

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Video transcript

- [Instructor] So let me start with an interesting question. Pause this video and try to figure out how many of these blocks are shown right over here? All right, now let's work through it together. Now you might have noticed that they have been organized in interesting ways. So you just have regular blocks here. Let's see, here you have one, two, three, four, five, six, seven, eight, nine individual blocks. And so I'll just write that there. And then over here, these blocks have been arranged into these bars or these stacks where each stack has one, two, three, four, five, six, seven, eight, nine, 10 blocks. And so really, the number of bars we have here, since each of them have 10 individual blocks in it, that tells us how many tens we have. So we have one 10, two tens, and three tens. So this right over here, you could either view it as three tens, or you could view it as 30 blocks. So let me just write it like this, three tens. I wrote it in the tens place. So so far between these and these individual blocks, we have three tens and nine ones. So far we've counted 39. And now what about these sheets? Well you might notice that these sheets have 10 rows and 10 columns. And if you were to count all of the blocks in one of these sheets, you will see that you have 10 groups of 10 which is the same thing as 100. That's 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100. So each of these sheets have 100. And then how many of these hundreds are there? Well, you clearly count one sheet and then another sheet. So we have two hundreds here. So I'll just write that in the hundreds place. So we have a total of two hundreds, three tens, and nine ones, or 239 blocks. Now let's go the other way. Let me show you some blocks and ask you which of these groups of blocks, this brownish-yellow color version, all of these blocks, or this purple one, which of these shows 923 blocks? Pause the video and see if you can figure that out. All right, so you might getting the hang of it now, you just have to look at how many hundreds, how many tens and how many ones. So let's look at this yellow one right over here. And so we can count these sheets to figure out how many hundreds. So we have one, two, three, four, five, six, seven, eight, nine. So we have nine hundreds. Just like that, which we could also write as 900. And then, how many tens do we have? We could see one, two, three tens. So plus three tens which is the same thing as plus 30. And then, how many ones do we have? Well, one one and two ones. So plus two ones. So that's the same thing as plus two. Or we could say in the hundreds place, let me just put the places here. So that's hundreds, tens, ones place. In the hundreds place, we have nine hundreds. In the tens place, we have three tens. And in the ones place, we have two ones. So this isn't 923, this is 932. So it's probably going to be this one, but let's see if we can figure that out. And let's just go straight to putting them in the appropriate place. So we immediately see, if we just count the individual blocks that haven't been put into a rod or a sheet, we can see there's three ones. So let's put that in the ones place. And then, we can see that we have two rods. Each of them have 10. So there's two tens right over there. So we can just write that in the tens place, two tens. And then, how many hundreds do we have? Well we have one hundred, two hundred, three hundreds, four hundreds, five hundreds, six hundreds, seven hundreds, eight hundreds, nine hundreds 'cause each of these sheets has 100 blocks in it. So nine hundreds, we could just write a nine in the hundreds place. So this last one is, this is another way to represent 923.