Lesson Plan - Get It!
You and your friends are racing around a football field. The field is 100 yards long and 50 yards wide. How many yards will you have to run to get all the way around the field?
The perimeter is the length or distance around the outside of a shape.
The perimeter is found by adding up the lengths of all of the sides of a figure. Perimeter is used when you are walking around the border of something, like a football field. Perimeter is also used to build a frame around a picture, seat guests around a table, or to make sure you have enough wire or fencing for a backyard.
Watch this short video to learn how to find the perimeter of various shapes using metric measurements: Perimeter Song.
How do you find the perimeter of a rectangle if only two of the side lengths are labeled? Discuss with your parent or teacher.
Remember, perimeter is the distance around a two-dimensional shape.
Find the perimeter of the following shapes:
The first shape is a square. What do you remember about the side lengths of a square? Discuss with your parent or teacher.
The side lengths of a square have the same measurement. If one side length is 6 cm., then the other 3 sides are 6 cm. To find the perimeter, we will add 6 + 6 + 6 + 6 = 24 cm. Sometimes, the perimeter of a square is also found by multiplying one side length by 4, since all of the sides have the same measure. If you follow that method, you would do 6 x 4 = 24 cm.
Find the perimeter of this rectangle. Since a rectangle has four sides, the measurement of each side needs to be known before the perimeter can be found. What do you know about the opposite sides of a rectangle? Can you find the missing measurements? Discuss with your parent or teacher.
The opposite sides of a rectangle are equal in measure. If the length is 7 inches, then the opposite side is also 7 inches. The width is 1 inch, so the opposite side is also 1 inch. Since there are four sides to a rectangle, to find the perimeter, you will need to add four numbers. Perimeter of a rectangle = length + length + width + width, so 7 + 7 + 1 + 1 = 16 inches. Sometimes, the formula 2x(length +width) is used, but you will get the same solution.
Find the perimeter of the hexagon. A hexagon has 6 sides. In this figure, all 6 sides are labeled in inches. To find the perimeter, add up the six values: 7.1 + 4 + 4 + 7.1 + 4 + 4 = 30.2 inches. Perimeter can be in decimals, fractions, or whole numbers. Don't forget to always include the measurement label in your answer!
Discuss with your parent or teacher:
- How do we find the perimeter of a square?
- How do we find the perimeter of a rectangle if all the side measurements are not given?
- What is an example of how perimeter is used in real-world situations?
Now that you are familiar with how to find the perimeter of shapes, move to the Got It? section to practice perimeter with games and interactive activities.