Prior to taking students outside for the hands-on part of this lesson, either teach students about or remind them of the very direct relationship between finding the area of a rectangle and using arrays in multiplication. If the idea of perimeter has not yet been introduced, explain the difference between area and perimeter. One tried and true classic is to compare the area of the classroom to the floor space covered by tile or carpet, and the perimeter to the distance a number line or border would cover if it went all around the tops of the classroom's walls.
Here is an example that differentiates between area and perimeter and shows how to find the area and perimeter of a rectangle: Examples of Area and Perimeter On Level and Examples of Area and Perimeter Enrich.
These student practice pages (Student Practice Find Area and Perimeter Extra Support, Student Practice Find Area and Perimeter On Level, and Student Practice Find Area and Perimeter Enrich) can either be printed, projected, or accessed by students on individual computers.
If you have leveled your students, you may want to break them into groups based on the type of practice they need. Ideally, each child should have a meter or yard stick for this activity. Whatever they have, make sure they are using consistent units, either yards or meters.
Give the students some of the following questions/prompts and circulate around the group(s) to ask them to explain their thinking and to assist them in kindly critiquing the reasoning of others. Also prompt them to recall the basic facts, addition and subtraction, involved in answering these problems.
What is one way to make a room with a perimeter of 12? What is the area? What is another way to make a room with a perimeter of 12? Is the area the same? Why or why not?
* Would this room be large enough to be used as a... (classroom, bedroom, closet, and so on).
Make a rectalinear room with a perimeter of 24. What is the area? What would be another way to make a room with a perimeter of 24? What is the area of this second room? If one of these rooms needed to be used as a classroom for a small group tutoring room, which room would be better suited to this purpose? Why?
Here is an example of students creating a room: Area Outside
When asked how many kids will fit in classroom, the students choose an interesting way to determine how much space is needed for each child.
This video clip shows a student critiquing the reasoning of another student. The students are building a room for an (imaginary) orphanage and have the idea that if they can sit in the room, then it is a big enough space. This child draws the line at a nursery that has extremely small dimensions.
Here is one more example of a child explaining his reasoning.
Have the students think (silently) of something new they discovered or were able to explain today. Ask them to either write this concept down to share with an adult at home or have them share with one or more other students using an inside-outside line.
An inside-outside line is my tiny classroom version of the Inside Outside Circle.