Lesson Plan

Parallel and Perpendicular Slopes

Determining from a pair of equations if two slopes are parallel, perpendicular or neither, and also graphing equations that are parallel or perpendicular
Anthony I.
Classroom teacher
Carlynton Junior/Senior High School
Carnegie, PA
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My Grades 7, 8, 9, 10, 11, 12
My Subjects Math

Students will be able to...

  • Graph Parallel and Perpendicular equations
  • Recognize when two lines are parallel or perpendicular
  • Write a set of equations that are either parallel or perpendicular
Grades 8 - 10
All Notes
Teacher Notes
Student Notes

1 Anticipatory Set/Hook

1. Prior to the lesson, the teacher should create a set of Plickers questions asking the following question: "How would you describe these lines?" with attached pictures being different pairs of lines.  The answer choices should be: parallel, perpendicular, neither, impossible to tell.  (Obviously, the teacher should also set up an account with Plickers, and assign each student to a different numbered card.)

  • Included in the plickers questions should be two lines that appear to be parallel and two lines that perpendicular, but can't be certain since the students don't know about their slopes yet.

2. Make sure students are given their card (or pick them up as they come into the classroom).

3. Show each question, and direct students to face the corresponding side of their Plickers card up to indicate the answer they believe is correct.

4. Repeat step three until all questions have been completed.

5. Begin discussion on how the students know that two lines are parallel or perpendicular.  Use this to springboard the students to realize there is a more surefire way to know if two lines are parallel and perpendicular -- their slopes.

Student Instructions

1. Pick up Plickers cards upon entering classroom.

2. Answer series of questions provided by the teacher.

3. Engage in discussion about how the students know that two lines are parallel or perpendicular

2 Procedures


1. Using a pre-made presentation, instruct students to graph two equations (that are parallel) on a piece of graph paper.

2. Ask students what they notice about the graph (that they're parallel) and follow up by asking how they could tell just by looking at the equations.

3. Formally introduce that two equations are parallel when their slopes are the same.

4. Repeat steps 1 & 2 with two equations that are perpendicular.

5. Formally introduce that two equations are perpendicular when their slopes are negative reciprocals of one another.


6.  Assign students a short set of problems that includes graphing lines (parallel, perpendicular and neither) and identifying lines from equations (parallel, perpendicular and neither).

  • While students work on the independent practice, roam around the room, answering any questions the students may have and quashing any misconceptions.


7. Assign students (pre-made) Google form questions about whether two lines are parallel, perpendicular or neither.  This can function as a class work assignment or as a short quiz.

Student Instructions

1. Follow along with the teacher throughout the guided practice section, participating in discussions and in graphing the pairs of equations.

2. Complete the short independent practice assignment individually, asking questions of the teacher.

3. Complete Google Form questions on iPad.

3 Closure

Free, Free to Try

1. Discuss real-life parallel and perpendicular lines.

2. Show Tellagami assignment/example either created by teacher or using this pre-made one:

The short project can be done by taking pictures and using the tellagami app on the iPads, or done at home using the students' devices.

3. Be available for student questions on how tellagami works, and possible misconceptions on parallels/perpendiculars.

Student Instructions

1. Engage in discussion about real life parallel and perpendicular lines.

2. Watch assignment video that gives a good overview of closure project.

3. Take pictures, create avatar and record voiceover of 30-second tellagami video to be turned in by the next class showcasing parallel and perpendicular lines in real life.