This is an intervention lesson. Most of my students come into 7th grade with a very weak model for understanding area and perimeter. Students can recite the formulas or procedures, but can't tell when either of them is used or give a definition. When asked to find the area students often give the perimeter or give both area and perimeter trying to hedge their bets. Often they will mix the two procedures up and multiply ALL of the sides or add only two. In addition, students don't understand the distinction between square or linear units of measure.
This comes after several contextual lessons that have helped students understand better the definitions of area and perimeter and the context in which they are used. In this lesson students create a foldable that I call "shutter" that will contain the definition, my graphic reminder, sample problems on grid paper, several strategies that they have already explored in earlier lessons, context, and units, as well as their own graphic reminder.
Even though my students may not open a math book as reference they are more likely to refer to this resource because they make it. In order for this to be useful to students I have to remind them to take them out in the next few lessons so they get into the habit of referring to it.
For their warm up I give them a small piece of graph paper and ask them to draw one rectangle that has an area of 6 square units and a perimeter of 10 linear units. If students ask what linear units are I just tell them to focus on the rectangle's area and perimeter and they will discover it in a moment. As students are finishing their rectangles I ask them to hand it to someone else so they can check that the rectangle does indeed fit the criteria. I expect several students to draw a rectangle with a length and width of 6 and 10. Some "checkers" will catch the mistake and some won't. When most groups are at the checking phase I will ask what they should count to check the area. When they say the "squares on the inside" I ask how many they should find. This should be enough to get the rest of the students to see the error and correct their drawing. Often I hear a lot of "Oh!" and I may see students grabbing their graph papers back to correct them.
Then I show them a 6 by 10 rectangle that I drew and ask them how I did. They love correcting my mistake!
After handing out the blank shutter template I ask students to fold it in half with the writing inside using a "hamburger" (vs. a hotdog) fold. I recently learned this from an elementary teacher friend and all my students knew what I meant! Then students fold the top and bottom into the center which I demo on the doc cam. Before they start writing it is important for them to make sure the shutters are right side up or else all of the writing will be upside down and the area examples will be under the perimeter flap...a real mess. I put a star in the upper right hand corner to help them orient.
Starting with the shutters closed students write the words area and perimeter on the two flaps. They copy my definition for each and draw my visual graphic. On the inside, under the appropriate flap, students copy down the strategies and formulas we have worked with, examples of correct units, and some contextual examples for when area and perimeter are used. Then we work through and label examples using the strategies on the inside grid.
Students will finish with their own graphic in tomorrow's lesson. I don't want students to make the shutters and then put them away for good. Once they have made a resource it is important for them to use it right away!
I want to give them a few minutes at the end of class to use their new resource. The directions in their homework tell them to use the shutters they just made and tell them to pay particular attention to double checking their units. By telling them a specific way in which to use their shutters, I think it will reinforce their use. I will remind them again to take them out tomorrow too!