Lesson 3
Plot More Points
Warm-up: Notice and Wonder: Points with Zero (10 minutes)
Narrative
The purpose of this warm-up is for students to think about points on the axes. In previous lessons they have plotted points with non-zero coordinates. Thinking about the points with zero prepares them for plotting points on the horizontal and vertical axes which they will do in this lesson.
Launch
- Groups of 2
- Display the image.
- “What do you notice? What do you wonder?”
- 1 minute: quiet think time
Activity
- “Discuss your thinking with your partner.”
- 1 minute: partner discussion
- Share and record responses.
Student Facing
What do you notice? What do you wonder?
Student Response
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Activity Synthesis
- “How can we describe the location of the point?” (It is at the bottom left of the grid.)
- “The coordinates of this point are \((0, 0)\). What would be the coordinates of the point if we moved it up 2 units?” (0, 2)
Activity 1: What’s the Point? (20 minutes)
Narrative
The purpose of this activity is for students to plot several points with the same vertical or horizontal coordinate and observe that they lie on a horizontal or vertical line respectively (MP7). Students also plot points on the axes for the first time. Before plotting the points on a grid with gridlines, students first estimate the location of the points. This encourages them to think about the coordinates as distances (from the vertical axis for the first coordinate and from the horizontal axis for the second coordinate).
Advances: Conversing, Representing
Supports accessibility for: Organization, Conceptual Processing, Language
Launch
- Groups of 2
- “You and your partner will each complete a different set of 4 problems independently. After you’re done, discuss your work with your partner.”
Activity
- 5–7 minutes: independent work time
- 5 minutes: partner discussion
- Monitor for students who:
- use the halfway point on each axis as a benchmark for the coordinate grid without gridlines
- start at zero and count spaces along each axis for the marked coordinate grid with gridlines
- recognize the points should be aligned because they share a common horizontal or vertical coordinate
Student Facing
Partner A
- Estimate the location of each point.
Point Coordinates \(A\) \((5,1)\) \(B\) \((5,2)\) \(C\) \((5,3)\) \(D\) \((5,4)\) -
Plot and label the points on the coordinate grid.
- What do the points have in common?
- Plot the point with coordinates \((5,0)\) on the coordinate grid.
Partner B
- Estimate the location of each point.
Point Coordinates \(A\) \((4,3)\) \(B\) \((5,3)\) \(C\) \((6,3)\) \(D\) \((7,3)\) -
Plot and label the points on the coordinate grid.
- What do the points have in common?
- Plot the point with coordinates \((0, 3)\) on the coordinate grid.
Student Response
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Advancing Student Thinking
If students do not reasonably estimate a location for a point on the blank grid, point to the location half way between 0 and 5 on the horizontal axis and ask, “What number might go here?”
Activity Synthesis
- Ask previously identified students to share their thinking.
- “What can we say about a set of points when they share the same first coordinate?” (They will be on the same vertical line.)
- Display image from student solution showing points with first coordinate 5.
- “How did you know where to put the point with coordinates \((5,0)\)?” (I put it on the horizontal axis. I went over 5 but did not go up at all.)
- “What happens when a set of points share the same second coordinate?” (They will be on the same horizontal line.)
- Display image from student solution showing points with second coordinate 3.
- “What does the zero in (0,3) tell us?” (It means the point will be on line zero of the horizontal axis, which is the vertical axis.)
- “\((0, 0)\) is an important point because it's where we start when we plot a point on the coordinate grid. Find \((0, 0)\) on the grid you have been working with.”
Activity 2: Plotting Points Without a Grid (15 minutes)
Narrative
Launch
- Groups of 2
Activity
- 3–5 minutes: independent work time
- 5 minutes: partner discussion
Student Facing
-
A point is labeled in the coordinate plane. Plot and label some other points. Explain or show your reasoning.
- Can you plot \((1,0)\) and \((0,1)\) accurately? Explain or show your reasoning.
Student Response
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Advancing Student Thinking
If students need support getting started with the task, ask, “What do you know about the point \((4,2)\) that is plotted?”
Activity Synthesis
- Invite students to share the points that they plotted and their reasoning.
- Plot the points as they discuss their reasoning.
- “How did you plot \((1,0)\)?” (I know where \((2,0)\) is on the vertical axis because it has the same horizontal coordinate as \((2,4)\). Then I just halved the distance to the vertical axis and that's \((1,0)\).)
- “Once you know where \((1,0)\) is, what other points can you locate on the vertical axis?” ((2,0), (3,0), (4,0),... I can just keep marking off that distance like I do when I am on a number line.)
Lesson Synthesis
Lesson Synthesis
“Today we plotted points that lie on the same horizontal or vertical line, including the horizontal and vertical axes.”
Display the first image from student A solution in first activity.
“Do these points have the same horizontal coordinate or vertical coordinate? How do you know?” (They all sit over the same place on the horizontal axis. That tells you the horizontal coordinate and it’s the same for all of the points.)
“Do any of the points have vertical coordinate 0? How do you know?” (No, if the vertical coordinate were 0, the points would be on the horizontal axis.)
“In the next section, we will be exploring rectangles and other quadrilaterals and sometimes we’ll put them on the coordinate grid.”
Cool-down: Missing Coordinate (5 minutes)
Cool-Down
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Student Section Summary
Student Facing
In this section, we plotted and described points on the coordinate grid.
The point \(P\) is 4 units from the vertical axis and 2 units from the horizontal axis. Its coordinates are \((4, 2)\). The point \(Q\) is 0 units from the vertical axis since it is on the vertical axis. It is 7 units from the horizontal axis. Its coordinates are \((0, 7)\).
The first coordinate of a point tells us its horizontal position and the second coordinate gives its vertical position.