Students will learn about perimeter and the units used to measure perimeter using a variety of materials including their hands, feet, rulers, and computer applets.

Upon completion of this lesson, students will:

• have practiced finding perimeter of rectangular shapes and irregular shapes with right angles.
• understand which units of measure are appropriate for measuring perimeter.

Technological: Students must be able to:
• perform basic mouse manipulations such as point, click and drag
• use a browser for experimenting with the activities

Students will need:

• access to a browser
• construction paper and pencil
• rulers and graph paper

1. Focus and Review
   Motivate the lesson by asking the students if anyone has a fenced yard and ask them to think about how you might figure out how much fencing was required.
   
   
   
2. Objectives
   Students will be able to demonstrate their knowledge of perimeter by calculating the perimeter of computer generated shapes.
   
   
   
3. Teacher Input
   
   • Have the class measure the perimeter of their desk top using their hands as the unit of measure.
   • Discuss the different answers the students calculated.
   • Discuss why the answers differed.
   • Introduce the term perimeter.
   
   
4. Guided Practice
   
   • Have the students work in pairs and measure the perimeter of 4 or 5 different objects around the room using different units: hands, feet, pencils, in, ft, etc.
   • Monitor the students' progress.
   • Have a couple of students share their examples.
   • Discuss why it might be necessary to have a standard unit like: inches, feet, or meters.
   • Discuss why someone might need to know the perimeter of something. (Example: fencing a yard)
   • Demonstrate how to use the Perimeter Explorer. (You may want to specify certain area settings.) Have the students answer a couple of computer generated problems with you.
   • Demonstrate how to draw the figure generated by the computer on a piece of graph paper.
   
   
5. Independent Practice
   
   • Have the students work either alone or in groups of two with the Perimeter Explorer.
   • So you can check their progress, have the students copy the computer generated figures on a piece of graph paper.
   
   
6. Closure
   
   • Draw a grid on the board and draw a few shapes in the grid.
   • Call on several different students to help you determine the perimeter of each shape.
   • Review the meaning of the word perimeter.
   • Review the different units used to measure perimeter.