Rational Numbers as Points on the Number Line and Coordinate Plane
For number line problems, identify the unit and subdivision. For coordinate plane problems, name the quadrant before plotting or locating the point.
Recall / Warm-Up
On a number line from 0 to 2, where would you place the fraction ?
A point is located at (3, 5) on a coordinate plane. In which quadrant is it?
What is the opposite of 7 on the number line?
Fluency Practice
On a number line, a point is located 2.5 units to the left of 0. What is the signed number for this point?
What is the opposite of ?
On a number line subdivided into thirds, where is the point ?
If , what is ?
In which quadrant is the point (−4, 3)?
Varied Practice
Which rational number is located between and on the number line?
The opposite of is ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ . This means .
Which statement about is always true?
The point is in Quadrant ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ . Its reflection across the x-axis is the point ( ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ , ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ).
The point (−2, 5) is reflected across the y-axis. What are the coordinates of the reflected point?
Word Problems
A number line is subdivided into fourths. Point P is located at and point Q is located at .
How far apart are points P and Q? (Count the fourths between them.)
Points A(3, 4), B(−3, 4), C(−3, −4), and D(3, −4) are plotted on a coordinate plane.
Which quadrant contains point C(−3, −4)?
Complete the description.
The points have the same ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ -coordinate and opposite ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ -coordinates.
The transformation from A to B is a reflection across the ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ -axis.
A coordinate plane is used to map a garden. The origin (0, 0) is a birdbath. The rose bed is at (−2.5, 1.5).
What are the coordinates of the point that is the reflection of the rose bed across the x-axis?
Error Analysis
Carlos evaluated when and wrote: ' because there is a minus sign in front, so the answer must be negative.'
What error did Carlos make?
Yuki was asked: 'What is the reflection of the point across the x-axis?' She answered: ' — I change the x-coordinate because I''m reflecting across the x-axis.'
What error did Yuki make?
Challenge / Extension
Point P is at (−3/2, 2) on the coordinate plane.
What are the coordinates of the point that results from reflecting P first across the y-axis and then across the x-axis?
Explain why . Use the meaning of 'opposite' in your explanation.