This perimeter geometry game was inspired by this short conversation with a 4th grader:
- Me: What’s perimeter?
- 4th grader: It’s where when the two sides are the same, then you um, I mean you times them by two.
- Me: Ok…I see where you’re going with that. But what does perimeter mean?
- 4th grader: I know, but I can’t really explain it.
A lot of kids learn perimeter and area as just rules to be memorized. When they don’t grasp the concept, they get confused and are likely to mix up the “area” rule with the “perimeter” rule–without really understanding either of them.
This geometry game gives kids real hands-on practice with perimeter–and gets them asking some questions about area, as well.
Perimeter: the distance or measurement around the outside of a two-dimensional shape.
How To Play “The Perimeter Game”
Players: 2 to 4
Best for: Understanding the concept of perimeter and area
- Roll the die and take that many tiles.
- Arrange your tiles to make a shape. Each tile in the shape must have at least one full side touching another tile.
- Add up your perimeter after each roll. (Count each outside edge of the squares in your shape.)
- On each new roll, add to your shape and count the new perimeter.
Some kids find it helpful to write the numbers to help keep track as they add up perimeter. (In case you’re wondering, the wipe-off grid you see in the picture is actually the back of a these hundred charts.)
- As you get closer to 24, you can choose to roll OR move one tile in your shape. (Moving a tile can increase or decrease the length of the perimeter.)
- The first person with a perimeter of exactly 24 wins.
Getting The Most From This Geometry Game
We kept playing even after the first person got a perimeter of 24 to see who would get second place, third place, and so on.
I asked the winners who were no longer playing to take a picture of their creations and to count how many squares they used (the area).
They also wanted to name their pictures. We had a robot and a torch, among other things.
This gave the other kids time to finish their game and work out how to get to a perimeter of 24–even if they initially went over.
At the end of the geometry game, I asked them some questions:
- What did you notice when you were doing this activity?
- The robot and the torch both have a perimeter of 24, but the robot used 11 squares and the torch used 15. How can that be?
- How would you change your shape if you wanted less of a perimeter? How would you get more of a perimeter?
NOTE: Counting outside squares to find perimeter is more challenging than it seems. As you help kids count, be very clear about the starting place, so they know when they have made it all the way around their shape.