Perimeter: Add Around

Lesson Plan - Get It!

Audio:

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.