Title – Perimeter of Real World Objects

By – Teresa Cummings

Primary Subject – Math

Grade Level – 3rd

Standards:

SC Math Standards 2007 – Measurement
3-5.5 Generate strategies to determine the perimeters of polygons.

Objectives:

Students will demonstrate their knowledge of how to use tools such as a ruler or yardstick to find the perimeter of objects around the classroom.

Materials:

• Cards numbered 1-5
  
• Five classroom objects
  
• Pencils
  
• Stopwatch
  
• Rulers & yardsticks (at least 10 of each)
  
• Record sheets to record perimeter of each object
  
• White board/dry erase markers

Procedures:

Prior to class: Teacher should have cards numbered 1-5 and each card should be taped onto a different object in the classroom that students will find the perimeter of.
1. Teacher will write the word “perimeter” on the board and ask students what they think it means by just by the word itself.

2. Teacher will explain that the “perimeter” of an object is the length of all of its sides added together.
   
   Practically speaking, you could think of it as the distance you would have to walk to go around a large object like a house or farm yard or the length of string you would need to go around a small object.
   
   Teacher will write the first explanation on the board.

3. Teacher will draw a rectangle on the board with a length of 4 inches and a width of 5 inches. Teacher will ask for a student volunteer to come up and find the perimeter of the rectangle.

4. When all the sides are added together the student should get an answer of 18 inches.

5. Teacher will then draw a square on the board and ask for a student volunteer to first find the length of each side, and then find the perimeter. (Students should realize that since all 4 sides of a square are equal they should only have to use the ruler to measure one side.)

6. Teacher will explain the next activity which is for students to be put in groups and find the perimeter of objects around the classroom.
   1. Teacher will put students into five groups (since there are five different stations)
      
   2. Teacher will distribute a record sheet, two rulers and two yardsticks to each group.
      
   3. Teacher will explain that each group will begin at a different station and on the teacher’s signal they will measure the length of the sides to the nearest ½ inch and find the perimeter of what ever object is at their station.
      
   4. Teacher will also explain that students only have five minutes at each station and that he/she will be timing them with a stopwatch. Once five minutes is up, the teacher will stop them and the groups will rotate to the next station.
      
   5. The activity will continue until every group has been to every station.

7. Once all the groups have visited each station the class will come back together.

8. Teacher will ask students what they got for the perimeter of each object.

9. If some of the answer vary slightly (which they probably will), teacher will talk about how it might be due to using different rulers or to different people reading the measurements.

10. Teacher will conclude lesson by restating that the perimeter of a polygon is the length of all of its sides added together and collecting students’ record sheets.

Homework:

A worksheet with different types of shapes (with the length of the sides given) that students must find the perimeter of.

Assessment:

Teacher will walk around during the activity and observe students measuring the different objects and finding their perimeter. Teacher will also look at the record sheets to make sure students can correctly calculate perimeter.

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Teresa Cummings

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