Coordinate Plane — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
The y-axis is the horizontal line on a coordinate plane.
Corrected: The y-axis is the vertical line on a coordinate plane.
The y-axis runs up and down (vertically), not side to side. The horizontal line is the x-axis.
2. Fix the sentence:
The ordered pair (0, 9) is located 9 units to the right of the origin.
Corrected: The ordered pair (0, 9) is located 9 units up from the origin.
Since the x-coordinate is 0, you don't move right at all. The 9 is the y-coordinate, so you move 9 units up from the origin.
3. Fix the sentence:
In the ordered pair (x, y), the second number tells how far to move right.
Corrected: In the ordered pair (x, y), the second number tells how far to move up.
In an ordered pair (x, y), the first number tells how far right and the second tells how far up. Moving right is the job of the x-coordinate, not y.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. In the ordered pair (5, 9), the x-coordinate is 5.
The x-coordinate is always the first number in an ordered pair, so in (5, 9) the x-coordinate is 5.
2. The ordered pair (8, 0) lies on the x-axis.
When the y-coordinate is 0, the point sits directly on the x-axis because there is no upward movement from that axis.
3. To plot (4, 6), move 4 units right and 6 units up.
The x-coordinate 4 tells you to move 4 units to the right from the origin before moving up.
4. A point with a y-coordinate of 0 lies on the x-axis.
A y-coordinate of 0 means no vertical movement, so the point stays on the horizontal x-axis.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. What do all points on the x-axis have in common? Give an example.
Sample answer: All points on the x-axis have a y-coordinate of 0. For example, (5, 0) sits on the x-axis because you move 5 units right but 0 units up.
A good answer includes: All points on the x-axis have a y-coordinate of 0. For example, (5, 0) sits on the x-axis because you move 5 units right but 0 units up.
2. Carlos plotted the point (7, 3) by moving 3 units right and 7 units up. What mistake did he make?
Sample answer: Carlos switched the coordinates. The first number is the x-coordinate, so he should move 7 units right. The second number is the y-coordinate, so he should move 3 units up. The correct plot goes 7 right and 3 up.
A good answer includes: Carlos switched the coordinates. The first number is the x-coordinate, so he should move 7 units right. The second number is the y-coordinate, so he should move 3 units up. The correct plot goes 7 right and 3 up.