Perimeter - Measuring Arounnd
Lesson 8 of 8
Objective: SWBAT measure and solve problems for the perimeter of polygons.
To begin this lesson, I quickly do a review of some area problems and activities we used in earlier lessons. This included finding the area of rectangles and irregular polygons. I chose to present the area and multiplication concept before focusing on the perimeter measurements because I wanted the students to develop a clear understanding of each concept especially in the use of multiplication for area and addition for perimeter. Although area and perimeter are both Common Core measurement standards, I felt it was important to teach these standards separately for my students.
The focus of this lesson is to look at rectangles and polygons to find the perimeter. I feel it is important to first introduce the vocabulary term and create some sort of connection through actions or gestures with the students. This gesturing helps the student to create and retain the meaning of concepts. In my classroom, I use both a hand gesture and kinesthetic movements. The kinesthetic movement involves the students walking the perimeter of the class, around individual table groups, and also around the perimeter of the playground. This activity engages the students, and it also allows them to make the real world connection. Although it takes extra time during the lesson to complete this, it is necessary to meet the objective of this lesson. The gesture is completed by creating a rectangle in the air and saying the four syllables of the word perimeter for each side of the rectangle.
Together with the students using whiteboards, rectangles are drawn with measurements on two of the sides. This also gives me the chance to ask students to write in the missing measurements and do a quick assessment of their knowledge of geometric shapes. This is an important observational assessment of my ELL students.
I continue this practice with different rectangles and squares. Once the students are working quickly through these examples, I add in irregular shaped polygons that include L shapes, and those resembling stairs. The focus of these shapes is to include each individual side as part of the perimeter.
To transition into the independent work of this lesson, I focus on the number 24 as the total. I ask the students to create different shapes on their whiteboards that will add up to 24. To demonstrate this I draw a rectangle that is marked with the longest sides as 10 and the shorter sides as 2. Then I ask the students to create their own shapes that add to 24. Most students will draw a rectangle, and I encourage students to draw irregular polygon shapes to add to 24.
Try It On Your Own
I chose to have the students work in partners to find the area of different shapes. The students are given the task of designing a fence for a back yard. The challenge is that each backyard has a different shape, but all of the yards are the same perimeter. The students are to create a backyard design unique from all others in an irregular polygon shape equaling 60 units. I chose not to give a standard or metric measurement, because the students will be creating their designs using unifix cube manipulatives. Using this tool will allow the students to design and modify to create a completed fence without extra openings. Once they have created the design with the cubes, the students will create the design on graph paper, label all sides, and show the numeric math sentence.
To close this lesson the student partners share their designs with the class. I always find that some sort of group discussion or presentation, allows students the opportunity to practice using math vocabulary and conversations that are academic in nature. These presentations also allow the students to show their understanding of the topic and help me make observational assessments of their understanding. I use this information to work with students for reteaching.
After the students give their presentations, I also have them glue their graph paper into their math journals as a reference.