Mission 18 · Unit 7

Coordinate Plane

6.NS.C.8 · Unit 8
Today's objective: Plot points in all four quadrants and find distances.
Need a hint?
Re-read the problem and underline the numbers and the question. Pick one representation (model, table, or equation), show your steps, and check that your answer makes sense for the situation.

The school is planning a new outdoor lunch area. The principal has a map on a coordinate grid where each square = 1 meter. Four possible table locations have been marked: A(3, 5), B(-4, 5), C(-4, -2), and D(3, -2). Your team must plot these points, connect them to form a rectangle, find the length and width, and calculate the perimeter of the lunch area.

x y -4 -3 -2 -1 1 2 3 4 5 5 4 3 2 1 -1 -2 -3 -4 0 A(3, 5) B(-4, 5) C(-4, -2) D(3, -2) 7 m (width) 7 m (height) Perimeter = 2(7) + 2(7) = 28 m

The Investigation

The Problem: Plot points A(3, 5), B(-4, 5), C(-4, -2), and D(3, -2) on a coordinate plane. Connect them in order to form a rectangle. Find the length of side AB (the width), the length of side BC (the height), and the perimeter of the rectangle. Then answer: how many square meters is the lunch area?

Visual Model: Coordinate Grid with Rectangle

Finding Distances on the Coordinate Plane Horizontal Distance (Side AB) A(3, 5) and B(-4, 5) have the SAME y-value Distance = |3 - (-4)| = |3 + 4| = 7 -4 3 7 units Vertical Distance (Side BC) B(-4, 5) and C(-4, -2) have the SAME x-value Distance = |5 - (-2)| = |5 + 2| = 7 y=5 y=-2 7 Perimeter and Area Perimeter = 2(7) + 2(7) = 14 + 14 = 28 meters Area = 7 × 7 = 49 square meters Quadrant Key: I (+, +) = top right   |   II (-, +) = top left   |   III (-, -) = bottom left   |   IV (+, -) = bottom right

Step-by-Step Investigation Guide

  1. Set up the coordinate plane. Draw x and y axes. Label the origin (0, 0). Number both axes from -6 to 6. Guiding question: Which direction is positive for x? For y?
  2. Plot the four points. Start at the origin each time. Move right/left for x, then up/down for y. Mark and label A, B, C, D. Guiding question: For B(-4, 5), do you go left or right first? Then up or down?
  3. Connect the points. Draw line segments A to B, B to C, C to D, D to A. Guiding question: What shape do you see? How do you know it is a rectangle?
  4. Find the width (AB). A and B have the same y-value (5). Width = |3 - (-4)| = |7| = 7 meters. Guiding question: Why can we subtract x-values when the y-values match?
  5. Find the height (BC). B and C have the same x-value (-4). Height = |5 - (-2)| = |7| = 7 meters. Guiding question: This rectangle is actually a square! How do you know?
  6. Calculate perimeter and area. Perimeter = 2(7) + 2(7) = 28 m. Area = 7 x 7 = 49 sq m. Guiding question: Is 49 square meters enough space for lunch tables?

Language Support: Key Vocabulary

Coordinate plane
A flat surface with two number lines (x and y) that cross at the origin.
Ordered pair
Two numbers (x, y) that tell the position of a point. Always x first, then y.
Origin
The point (0, 0) where the x-axis and y-axis cross.
Quadrant
One of four sections of the coordinate plane, numbered I, II, III, IV.
x-axis
The horizontal number line (left-right).
y-axis
The vertical number line (up-down).
Sentence Frames:

"Point _____ is in Quadrant _____ because the x-value is _____ and the y-value is _____."

"The distance between _____ and _____ is _____ because I subtracted _____ and took the absolute value."

"To plot (x, y), I start at the origin, move _____ on the x-axis, then _____ on the y-axis."

Multiple Representations

Approach 1: Plotting and Counting

Plot all four points on grid paper. Count the grid squares along each side. AB goes from x = -4 to x = 3, that is 7 squares. BC goes from y = 5 to y = -2, that is 7 squares.

Approach 2: Absolute Value Formula

For horizontal distance: |x1 - x2| when y-values are equal.
For vertical distance: |y1 - y2| when x-values are equal.
AB = |3-(-4)| = 7. BC = |5-(-2)| = 7.

Approach 3: Coordinate Table

List each point with its quadrant:
A(3,5) = Quadrant I
B(-4,5) = Quadrant II
C(-4,-2) = Quadrant III
D(3,-2) = Quadrant IV
The rectangle spans all four quadrants!

Team Roles

Facilitator Read the lunch area scenario. Make sure everyone understands (x, y) order. Call out each point for the Model Builder to plot.
Model Builder Draw the coordinate plane with labeled axes. Plot all four points accurately. Connect them to form the rectangle. Label all sides.
Precision Checker Verify each point is in the correct quadrant. Check distance calculations. Confirm perimeter and area formulas are applied correctly.
Reporter Prepare defense: name each point's quadrant, state the dimensions, and present the perimeter and area with full calculations.

Timed Lab Phases

Launch Phase
03:00

Read the scenario. Assign roles. Review how to read an ordered pair: x first, then y.

  • In (3, 5), which number is x and which is y?
  • What does a negative x-value mean on the grid?
  • Which quadrant has both values negative?
Checkpoint: Everyone can explain how to plot an ordered pair starting from the origin.

Draw axes. Plot all four points. Connect them to form the rectangle.

  • Is each point in the correct quadrant?
  • Do the four points form a rectangle when connected?
  • Label each vertex with its ordered pair.
Checkpoint: All 4 points plotted correctly. Rectangle drawn and labeled.

Calculate side lengths, perimeter, and area.

  • AB: |3 - (-4)| = ? meters
  • BC: |5 - (-2)| = ? meters
  • Perimeter = 2(length) + 2(width) = ?
  • Area = length times width = ?
Checkpoint: All calculations complete with units (meters, square meters).

Reporter prepares the defense using the coordinate grid as evidence.

  • "Point A is in Quadrant _____ because _____."
  • "The width is _____ because we calculated |_____|."
  • "The lunch area has _____ square meters, which is enough for _____ tables."
Checkpoint: Defense includes quadrant identification, distance calculations, and perimeter/area.

Challenge Extensions

Extension Problem: The principal wants to add a fountain at the exact center of the rectangle. What are the coordinates of the center point? (Hint: average the x-values and average the y-values.) Then find the distance from the fountain to the nearest corner.

What If?

  • What if point D moved to (3, -5)? Would the shape still be a rectangle? What would the new perimeter be?
  • Reflect the rectangle over the y-axis. What are the new coordinates of each vertex?
  • If each lunch table needs 4 square meters of space, how many tables fit in the 49 square meter area?

Real-Life Connections

Coordinate planes are used in GPS navigation, video game design, architecture blueprints, and mapping apps like Google Maps.

Defense Preparation

  1. Name the quadrant of each point. How do you know?
  2. How did you find the length of side AB? Show the absolute value calculation.
  3. Why does this shape span all four quadrants?
  4. What is the perimeter and area? Include correct units.
Sentence Starters:
  • "Point _____ is in Quadrant _____ because both its x and y are _____."
  • "We found the distance by subtracting coordinates: |_____ - (_____)| = _____."
  • "The perimeter is _____ meters because _____."

Rubric

Criteria Excellent (4) Proficient (3) Developing (2)
Plotting All 4 points in correct position with labels 4 points plotted, minor label issue Some points plotted
Quadrants All 4 quadrants correctly identified with reasoning Quadrants identified Some quadrants named
Distance Both distances with absolute value shown Correct distances stated Attempted
Perimeter/Area Both correct with units and formulas Correct answers One calculation correct

Exit Product

Your team submits: A Lunch Area Blueprint that includes:
  • A coordinate grid with labeled axes (at least -6 to 6 on both)
  • All four points plotted and labeled with ordered pairs
  • The rectangle drawn with side lengths labeled
  • Distance calculations for width and height using absolute value
  • Perimeter (28 m) and area (49 sq m) with formulas shown
  • Each point's quadrant identified

Self-Assessment Checklist