1. Lesson 20
Proportionality
The Coordinate Plane

2. Warm-Up
In a bag full of marbles, there were 6 green, 2 red and 4 blue marbles. If a marble is chosen from the bag and then returned, find:
P(green)
P(red)
P(blue)
P(not blue) 
The ratio of girls to boys in Ms. B’s class is 12 : 13. What is the ratio of girls to all students in Ms. B’s class?
Solve for y in the similar figures to the
right.

3. Target: Recognize and graph ordered pairs on a coordinate plane.
The Coordinate Plane
Target:
Recognize and graph ordered pairs on a coordinate plane.

4. Vocabulary x-axis: The horizontal number line on a coordinate plane.
y-axis: The vertical number line on a coordinate plane.
Origin: The point where the two number lines cross each
other at zero (0, 0).
Quadrants: The four regions formed by the x- and y-axes on a
coordinate plane.
Scatter Plot: A set of ordered pairs graphed on a coordinate
plane.

5. Example 1 Graph each point and name the quadrant where it is located.
a. A(4, 6)
Quadrant I
b. B(3, –2)
Quadrant IV
c. C(0, –8)
None, y-axis
d. D(–5, 7)
Quadrant II D A B C

6. Example 2abc Choose the letter with the given ordered pair. a. (5, 0)U
b. (– 4, 6) V
c. (–5, –2) R

7. Example 2def Choose the letter with the given ordered pair. d. (8, –7)

9. Example 3ab Use the table of values listed to the right.
a. Write the ordered pairs from the table using parentheses.
(–3, –6), (–2, – 4), (–1, –2), (0, 0), (1, 2), (2, 4), (3, 6)
b. Graph the ordered pairs on a coordinate plane.

10. Example 3c Based on your graph, if the x-coordinate is 6, what would
the y-coordinate be?
(6, 12)

11. Example 4
a. Make a scatter plot of the data. Label the x-axis “age” and the y-axis “height.”
b. Is there are relationship between the age of a person and the person’s height?
Yes, as the age increases so does the height.
c. Do you think this relationship will continue until someone is 70 years old? Explain.
No. People stop growing.

12. Exit Problems A B C
Write the ordered pair for each point on the graph at right.
a) A
b) B
c) C
Write the ordered pairs
for each point in the table. Graph the points. x y –2 –5 –1 –3 1 2 3

13. Communication Prompt What are the similarities and differences between
graphing the point (3, 7) and the point (–3, –7)?