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Measuring lengths in different units

Sal measures the same rectangle in different units and then compares the size of the different units. Created by Sal Khan.

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Video transcript

- [Instructor] So I have the same green rectangle up here and down here and what I wanna do is measure its width but we're going to measure it's with in two different ways. Up here, we're going to measure it's width in terms of how many of these paper clips wide the rectangle is and down here, we're going to measure its width in terms of how many centimeters wide this rectangle is. So let's start on top. Pause the video. How many paper clips wide is this rectangle? All right, now let's do this together. We can see that the rectangle starts right over here and it ends right over here on the right if we're thinking about its width and so we have one, two, three, four, five, six, seven, eight, nine, 10 paper clips. So this rectangle is we could say 10 paper clips, paper clips wide. Now, if we wanna measure it in terms of centimeters, we would do the same thing but we would use this ruler. Let me do this in a different color. So the left edge is there. The right edge is right over there and it looks like this rectangle is also one, two, three, four, five centimeters wide. Five centimeters wide. So notice 10, the same rectangle has the same width. It's 10 paper clips wide and it's five centimeters wide. So its width is more paper clips than centimeters is one way to think about it. Now, based on that, what is a larger unit of measurement, the paper clip, at least these paper clips or the centimeter? Pause the video to think about that. Well, you might just see it naturally if you just look at a centimeter right over here. It looks wider than a paper clip but you could also tell that by looking at the measurement. We needed more paper clips to cover the width of this rectangle than we needed centimeters and so, because we needed more paper clips, that means that this is a smaller unit of measure because we needed more of them. So this is a smaller unit of measure or maybe actually I should make the arrow point right over here. The paper clip is a smaller unit of measure and then the centimeter is the larger unit of measure. We needed fewer centimeters to make up the width of the rectangle than paper clips. So the centimeter is larger and you could see that visually if you just look at that with compared to that width. It's clear that a centimeter is wider than this paper clip.