Try 30 days for free

Discover why over 1.2 MILLION students choose sofatutor!

Finding Perimeter with Given Side Lengths

Rating

Ø 5.0 / 1 ratings

The authors
Avatar
Team Digital
Finding Perimeter with Given Side Lengths
CCSS.MATH.CONTENT.3.MD.D.8

Basics on the topic Finding Perimeter with Given Side Lengths

Content

Finding Perimeter with Given Side Lengths

It is summer time and in order to make summer evenings even better, your family wants to decorate the space around your pool with string lights. However, you will need to determine the perimeter of the pool in order to buy enough lights to string around the edges. This 3rd grade video and text teaches you how to find the perimeter of a shape with given side lengths. Continue reading if you want to learn how to solve for perimeter.

What Is Perimeter?

Let’s learn more about perimeter and how to calculate it in the following explanation.

Perimeter – Definition

The perimeter means the total distance around a figure, or the sum of all its sides. Finding the perimeter of any shape, regular or irregular, is simple: add up the lengths of each side to calculate the perimeter. The perimeter is always labeled using the correct unit of measure. Common units for perimeter might be centimeters, inches, feet, yards, meters, miles, and kilometers.

Perimeter units of measure

Perimeter vs. Circumference

Circumference is a special name given to a circle’s perimeter. However, finding the circumference requires a special perimeter formula. It is not just adding side lengths.

Finding Perimeter

The perimeter equals the sum of all a figure's side lengths. When finding a perimeter, begin by looking at the shape’s side measurements. For our pool, the sides are labeled fourteen feet, six feet, fourteen feet and six feet:

Rectangle with labeled side lengths

Next, write the equation for perimeter by adding all the side lengths together: 14+ 6 + 14 + 6:

Rectangle with perimeter equation

Then, determine the perimeter by calculating the sum and labeling with correct units. The solution to this perimeter problem is 40 feet. This means, we need to buy 40 feet of string lights for the pool area.

Rectangle with perimeter of forty

How to Find the Perimeter of Polygons – Formulas and Examples

In the table below are several examples of polygon perimeters.

Polygon Perimeter
triangle side 1 + side 2 + side 3
quadrilaterals:

square, rectangle, parallelogram, trapezoid, rhombus
side 1 + side 2 + side 3 + side 4
pentagon side 1 + side 2 + side 3 + side 4 + side 5
hexagon side 1 + side 2 + side 3 + side 4 + side 5 + side 6
octagon side 1 + side 2 + side 3 + side 4+ side 5 + side 6 + side 7 + side 8

For a better visual illustration, the following infographics show the perimeters of a pentagon, a hexagon and an octagon:

Pentagon with labeled side lengths

Hexagon with labeled side lengths

Octagon with labeled side lengths

How to Get the Perimeter – Summary of Steps

  • First, look at the figure's side measurements.

  • Next, write the equation for perimeter by adding all the side lengths together.

  • Then, determine the perimeter by calculating the sum.

  • Finally, label the answer with correct units.

Have you practiced perimeter problems yet? On this website, you can also find 3rd grade perimeter worksheets and exercises.

Transcript Finding Perimeter with Given Side Lengths

"I can't wait for our party tonight...it's going to be so much fun!" "Agreed, but don't you think we should decorate a bit?" "Hmmm, I see your point....let's see if the Flea Market has any string lights we can hang around the van, umbrella, and garden!" "So how many string lights will we need, Zuri?" Zuri and Freddie will have to determine the perimeter of each location in order to buy enough string lights for the party. Let's help them calculate the total by "Finding Perimeter with Given Side Lengths". The perimeter is the total distance around a figure or the sum of all its sides. Finding the perimeter of any figure is simple...we add up the lengths of each side to calculate the total measure. Perimeter should always be labeled using the correct unit of measure. Let's look at Zuri and Freddie's map to determine the perimeter of, or distance around, their van. First, we look at the figure's measurements...it says the van's sides are fourteen feet, six feet, fourteen feet and six feet. Next, we will write our equation by adding all the side lengths together: fourteen plus six plus fourteen plus six. Then, we calculate the sum...our total is forty! Finally, we rewrite our complete answer using the correct units... forty feet. Zuri and Freddie will have to buy forty feet of lights to string around the perimeter of their van. Now, let's find the perimeter of the umbrella...what does each side measure? Each of the six sides measures two feet. What is our next step? We write our addition equation: two plus two plus two plus two plus two plus two. Next, we add: What is the sum? The sum is twelve! What is our final step? The last step is to rewrite our complete answer using the correct units: twelve feet. Zuri and Freddie will have to buy twelve feet of lights to string around the perimeter of their umbrella. Lastly, let's look at the garden on the map: it says the different sides measure ten feet, five feet, eight feet, five feet, and ten feet. What is our first step? We write our addition equation: ten plus five plus eight plus five plus ten. What is the sum? The sum is thirty-eight! What is our final step? We rewrite the sum with the correct units next to our answer...thirty-eight feet. Zuri and Freddie will have to buy thirty-eight feet of lights to string around the perimeter of their garden. Remember, Zuri and Freddie want to buy string lights for each location, so we need to add up each of the perimeters. Let's add forty plus twelve plus thirty-eight. Forty plus twelve plus thirty eight equals ninety. They will need to buy ninety feet of string lights to have enough decorations. "I can't believe they had that many extra lights at the Flea Market!" Before we see how it all turned out, let's remember how they calculated the perimeters in the first place! First, identify the side lengths of the figure. Then, write an addition equation by adding up the measurements. Next, calculate the sum. Lastly, rewrite the sum with the correct units next to the perimeter. "Do you think its too much?" "Not a chance." "Yeah, it's perfect....no one will notice the land fill now."

Finding Perimeter with Given Side Lengths exercise

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video Finding Perimeter with Given Side Lengths.
  • What is the perimeter of the yard?

    Hints

    Remember, the perimeter is the distance around the shape. It is the total length of all the shape's sides.

    As an example, this is how you would find the perimeter for the rectangle below.

    Solution

    The perimeter of a shape is the distance around the shape.
    To find the perimeter, we must find the sum of the shape's sides by adding.

    10 + 15 + 10 + 15 = 50
    The perimeter of the yard is 50 yards.

  • How do you find the perimeter of a shape?

    Hints

    Looking at the picture of the rectangle, what step is first to find the perimeter?

    To find the perimeter, you must add the length of all sides of the shape.

    Remember- it is important to include the measurement units!

    Solution

    Perimeter is the distance around an object. To find the perimeter you must:

    1. Identify the side lengths and units of the figure.
    2. Write an addition equation by adding up the measurements.
    3. Add by calculating the sum of the sides.
    4. Rewrite the sum with the correct units next to the perimeter.
  • What is the perimeter of each shape?

    Hints

    The perimeter of a shape is the distance around the shape. It is the total length of the shape's sides. To find the perimeter, find the total length of the shape's sides.

    As an example, this is how you would find the perimeter for the shape below.

    Solution

    Perimeter is the distance around a shape. To find the perimeter, find the total length of the shape's sides.

    Rectangle: 7 + 20 + 7 + 20 = 54
    The perimeter of the rectangle is 54 inches.

    Triangle: 15 + 15 + 15 = 45
    The perimeter of the triangle is 45 inches.

    Square: 12 + 12 + 12 + 12 = 48
    The perimeter of the square is 48 inches.

    Rhombus: 13 + 13 + 13 + 13 = 52
    The perimeter of the rhombus is 52 inches.

  • What is the perimeter of each window?

    Hints

    The perimeter of a shape is the distance around the shape.

    Add the lengths of the sides to find the total distance around the shape.

    As an example, this is how you would find the perimeter for the shape below.

    Solution

    The perimeter of a shape is the distance around the shape. To find the perimeter find the total length of the shape's sides.

    Window 1:
    16 + 12 + 14 + 18 = 60
    The perimeter of window 1 is 60 inches.

    Window 2:
    14 + 28 + 14 + 28 = 84
    The perimeter of window 2 is 84 inches.

    Window 3:
    14 + 22 + 18 + 28 = 82
    The perimeter of window 3 is 82 inches.

  • What is the perimeter of the pentagon?

    Hints

    The perimeter of a shape is the distance around the shape. It is the total length of the shape's sides.

    To calculate the perimeter, you must find the sum the shape's sides. As an example, this is how you would find the perimeter for the shape below.

    Solution

    The perimeter of a shape is the distance around the shape. It is the total length of the shape's sides.

    To find the perimeter, add the lengths of each side of the pentagon.

    3 + 3 + 3 + 3 + 3 = 15

    The perimeter of the pentagon is 15 centimeters.

  • Which shapes have a perimeter of 24 feet?

    Hints

    More than one shape has a perimeter of 24 feet.

    Perimeter is the distance around a shape. As an example, this is how you would find the perimeter for the rectangle below.

    Solution

    The perimeter of a shape is the distance around the shape. It is the total length of the shape's sides.

    To find the perimeter:

    1. Identify the side lengths and labels.
    2. Add to find the sum, or total length, of the perimeter of the shape.

    Square:
    6 + 6 + 6 + 6 = 24
    The perimeter of the square is 24 feet.

    Rectangle:
    3 + 9 + 3 + 9 = 24
    The perimeter of the rectangle is 24 feet.

    Pentagon:
    5 + 5 + 5 + 5 + 5 = 25
    The perimeter of the pentagon is NOT 24 feet.

    Triangle:
    8 + 8 + 8 = 24
    The perimeter of the triangle is 24 feet.