# Measuring Our Classroom's Perimeter and Area!

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## Objective

SWBAT make reasonable estimates of ordinary rooms, such as the classroom, and then will calculate the perimeter and area.

#### Big Idea

Connect new measurement knowledge and skills to the students' immediate environment.

## Opener

10 minutes

I tell students that they will be measuring the area and perimeter of the classroom today.  (If your room is not rectangular, you might want to mentally cut off the parts that make it non-rectangular and settle for an estimated area, if not an estimated perimeter).  I ask students think and then share a few ideas for why a person might need to know the area of a room.  Ideas might include: amount of carpet, amount of floor cleaner, and the number of desks that will fit within it.  I ask the same question about the need for finding the perimeter of a room and again, here are some possible responses:  edging along the wall, how much of the wall would be taken up by a 30 foot long number line, how much border to decorate around the top, or how many chairs of a certain width could be fit around the edges of the room if we were performing in the middle.  Then students fill out the entrance side of the Measuring the Classroom Entrance Exit Ticket.

If you have a room like mine that is rectalinear but not a rectangle, I suggest demarcating the different sections that will need to be measured in order to calculate the area.  I use tape.

## Measuring the Classroom

25 minutes

Prior to making measurements of the room, students estimate the perimeter and width on the Measuring Our Classroom student page.

If your room is rectangular, it of course doesn't matter if the length and width are measured along the sides or through the center of the room.  My role in this part of the activity is to make sure all students are involved, and that they are following procedures for accurate measurement.  Rulers must be lined up end to end, so a team of 3 or 4 works well, as they can rotate being the place markers and the students moving the rulers forward.  While this can be done with the tape measure, working with 12 inch rulers is a natural opportunity to have them thinking about inches and feet.  This can also be done with centimeters and meters, or with both.

## Measuring the Cafeteria/Gym/Hallway

20 minutes

If there is time, I give students the chance to measure another room.  In one school I worked there was easy access to the gym, in my current school there isn't a gym, so a measurement of a section of hallway or any other room you have access to works as well.

## Wrap-up

5 minutes

I call the students back to the carpet at the conclusion of this activity to discuss some of their discoveries.  I provide these questions and question stems as scaffolding for both ELL students and for supporting precise mathematical language:

Was your estimate of the room's area close to the actual measurement?  Why or why not?

My estimated was/was not close to the actual measurement.

Why?  Why not?

I think that my estimate was not close to the actual measurement because…

I think one reason that my estimate was different from the actual measurement was because…

Which calculation was more surprising or interesting to you, area or perimeter?  Why?

I thought calculating the area was more surprising because I realized…

What do you consider a "close" guess?

I think a close guess would be…  if I was within…  if I was as close as…  if I was no more than --- away…

Do you think everyone has the same definition of what constitutes (makes) a "close" guess?

I do, do not think everyone has the same definition of what constitutes a close guess.