ALEX Lesson Plan


Lay It on the Line

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  This lesson provided by:  
Author:Susan Jordan
System: Mobile County
School: Mobile County Board Of Education
  General Lesson Information  
Lesson Plan ID: 33165


Lay It on the Line


This lesson allows students to explore their surroundings to locate and prove the presence of perpendicular lines. Students will use the corner of a ruler as a tester to determine right angles contained in classroom items. It can be included in a unit on geometry and measurement. 

This is a College- and Career-Ready Standards showcase lesson plan.

 Associated Standards and Objectives 
Content Standard(s):
MA2015 (4)
23. Recognize angles as geometric shapes that are formed wherever two rays share a common endpoint, and understand concepts of angle measurement. [4-MD5]
a. An angle is measured with reference to a circle with its center at the common endpoint of the rays by considering the fraction of the circular arc between the points where the two rays intersect the circle. An angle that turns through 1/360 of a circle is called a "one-degree angle" and can be used to measure angles. [4-MD5a]
b. An angle that turns through n one-degree angles is said to have an angle measure of n degrees. [4-MD5b]
MA2015 (4)
26. Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures. [4-G1]
MA2015 (4)
27. Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines or the presence or absence of angles of a specified size. Recognize right triangles as a category, and identify right triangles. [4-G2]

Local/National Standards:


Primary Learning Objective(s):

  • Recognize right angles in real-world figures.
  • Identify the presence of right angles as part of perpendicular lines. 
  • Recognize the differences between parallel and perpendicular lines. 

Essential Question: Where do I see perpendicular lines in real life and how can I prove it?

Additional Learning Objective(s):

 Preparation Information 

Total Duration:

31 to 60 Minutes

Materials and Resources:


  • Rulers
  • Protractors
  • Response Chart


  • One index card per student
  • Classroom Finds handout per student
  • Exit Slip per student

Technology Resources Needed:

  • Interactive whiteboard lesson (use attached pages for alternative displays if interactive whiteboard is not available.)


Students should know about angles and how angles are measured. They should have an understanding of degrees as a unit for measuring angles and that a right angle has a measure of 90 degrees.


1. Introduce lesson and show students the essential question attached below. (Standard may be stated if school does not use an essential question.)

2. Ask students what they know about right angles. Discuss and write students responses on the chart.

3. Display page with examples of angles. Go through each example and have students to tell whether it is right angle or not. Have students  justify why they think it is. Ask, “How can you tell?; Is there a way we can check? Is there a tool that we can use to check?” Review using a protractor as a tool. Make sure students know the symbol that indicates a right angle. (The square at the vertex of the angle.)

4. Ask students to discuss and record what perpendicular lines are on the response chart. Tell students they will learn more about them today in the lesson.

5. Discuss what they notice about right angles and perpendicular lines.

6. Display page with examples of perpendicular lines. Go through each example. Have students to tell whether the example has perpendicular lines or not. Students must explain how they know. If students are not sure, wait until after activity to readdress. Ask students if they see any examples of parallel lines.

7. Tell students perpendicular lines do not necessarily cross. Discuss with students that lines can still be perpendicular even if they do not extend or cross each other. (For example, a right angle is perpendicular rays that show only a portion of a full line.) Students can have a misconception about this since all of the line is not seen. Show the ‘extension’ of the line as dotted. Discuss this with students.

8. Tell students for today’s activity, they will use an index card to check for right angles. This might be a good time to talk about how it might be harder to physically check for right angles in the room with a protractor. Show students an index card and ask if they think there are any right angles in the index card. Use the protractor on the page to check and prove that there are actually 4 right angles.

9. Next, model for students how to use index card to check items. Make a point that it does not matter how big or small the object is, the angle measurement is the same. Teacher may need to discuss how objects with curved corners are not angles they should check.

10. Explain to students that they will work in pairs using the index card to look for and check for perpendicular lines in the classroom. Put students in pairs and distribute an index card and and handout on Perpendicular Lines in our classroom.  Tell students they will work together, but they will record on their own sheet. Suggest to students they should try to find different objects from the rest of the class if possible and that it is ok if they check some objects that the think may not have perpendicular lines. 

11. Tell students to pause silently for 30 seconds and to look around the room before they begin. Dismiss students to explore classroom. Teacher should circulate while students explore.  Make sure students are on task, give direction, and assess if students seem to know what they are looking for. 

12. Regroup as a class.  Allow each pair of students to share one object they explored Write their findings on the interactive whiteboard.  As students share, ask students, "How did you decide to check a particular object?; Did any of your objects have perpendicular lines that only showed rays of an angle?; Did you learn anything about perpendicular lines that we can add to the chart we started at the beginning of the lesson?"

13. Students should keep handout as a study reference.

14. Have students complete exit card.

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Assessment Strategies

Let students complete Exit Slip. The first part of the slip assesses whether students can identify perpendicular lines formed only from 2 lines.  The second portion assesses if students can identify them in other figures.


Have students to use index card to test objects in the room and classify as right, acute, or obtuse.


Teacher should assist students with activity that are having problems understanding. 

Each area below is a direct link to general teaching strategies/classroom accommodations for students with identified learning and/or behavior problems such as: reading or math performance below grade level; test or classroom assignments/quizzes at a failing level; failure to complete assignments independently; difficulty with short-term memory, abstract concepts, staying on task, or following directions; poor peer interaction or temper tantrums, and other learning or behavior problems.

Presentation of Material Environment
Time Demands Materials
Attention Using Groups and Peers
Assisting the Reluctant Starter Dealing with Inappropriate Behavior
Be sure to check the student's IEP for specific accommodations.