About this video
This video looks at two students who made mistakes plotting ordered pairs. Gisela plotted (4, 3) by going 4 right and 3 down, so her x-coordinate was right but her y-coordinate was wrong. Lucia plotted (8, 2) by going 8 up and 2 right, mixing up the x- and y-coordinates.
You'll be able to
- plot an ordered pair by moving right for the x-coordinate and up for the y-coordinate from the origin.
- spot and explain a mistake someone made when plotting a point.
- tell which coordinate in an ordered pair is x and which is y.
Key words
- ordered pair
- Two numbers written like (4, 3) that give the location of a point; the x-coordinate comes first.
- origin
- The point where the x-axis and y-axis meet; you start here to plot a point.
- x-coordinate
- The first number in an ordered pair; it tells how far to move right.
- y-coordinate
- The second number in an ordered pair; it tells how far to move up.
- coordinate grid
- A grid with an x-axis and a y-axis used to plot points.
Transcript
- [Instructor] We're told Gisela plots the ordered pair 4,3 on a coordinate grid by moving four units to the right and three units down from the origin. Which statement is true? So pause this video and have a go at this before we do this together. All right, now before I even look at the choices, let's just think about how we would approach it if we had to graph 4,3.
So let me draw some coordinate axes here. So that is my Y-axis. This right over here is my origin and that is my X-axis. So if I had to graph 4,3, the four coordinate is the X coordinate. So it says how much to the right do we move in the X direction? So I'm moving four from the origin to the right.
So let's say that that is four right over there. Maybe that's one, two, three, and then four. So I'd move four to the right and then the Y coordinate right over here says how much do I move up? So then I would move three up to get right over here. So maybe this is three right over here.
This would be one, two, and three to go here. So I'd go four to the right and then three up. Now it said that Giesla moved four units to the right. That's right, and three units down from the origin. So Gisela did something like this, four to the right and three units down and that does not make sense.
So let's see, A says Gisela did both of them correctly. That's not right. Gisela plotted the X coordinate incorrectly and the Y coordinate correctly. No, it's the other way around. Gisela got the X coordinate right. They went to the right but then should have gone up instead of down.
So this one isn't right. Gisela plotted both the X and the Y coordinate incorrectly. That's not right. Gisela, sorry, she got the four part right. She got the X coordinate correct. And then process of elimination, let's read this. Gisela plotted the X coordinate correctly.
That's right. She did the four to the right and the Y coordinate incorrectly. Correct. She went down when she should have gone up. So I like this choice. Let's do another example. So here we are told that Lucia tries to graph the 8,2 on a coordinate grid. She starts at the origin, moves eight units up, and then you moves two units to the right.
So let me just think about how I would do that. So if that right over there is my X-axis, this is my Y-axis, that's my origin right over there. And then let's see, if I had to deal with 8,2 that first coordinate right over there. The eight is the X coordinate.
It tells you how much to move to the right. So I would move eight to the right, let's say right over here, eight to the right and then the second coordinate is the Y. It tells you how much to move up. And then I would move two up. So I'd get to this point right over here.
So this is two. Eight to the right and then two up. Lucia went eight up and two to the right. So it looks like Lucia actually maybe confused the X and the Y coordinates. So let's see, which mistake did Lucia make? Lucia moved two units right instead of two units down.
No, it should have been moved two units to the right instead of two units up. I'll rule that one out. Lucia moved eight units up instead of eight units to the right. That one looks right, so I like this one. I will save that one. Lucia moved two units to the right instead of two units to the left.
No, this two right over here isn't talking about right or left. It's talking about how many units up. So rule that one out. Lucia moved eight units up instead of eight units down. No, it should have been eight units to the right, like we see in choice B, and we're done.
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