3rd Grade Math - Find Perimeter or Missing Side Lengths of Polygons: CCSS.Math.Content.3.MD.D.8

1

What is the perimeter of the rectangle below?

Screen shot 2015 09 29 at 8.31.53 am

Explanation

The formula for perimeter of a rectangle is

To solve for the perimeter we can plug our known values into the equation.

2

What is the width of the rectangle if the perimeter is and the length is ?

Explanation

The formula for perimeter of a rectangle is

To solve for the width we can plug our known values into the equation.

Subtract from both sides

Divide by both sides

3

What is the perimeter of the square below?

Screen shot 2015 11 05 at 8.21.29 am

Explanation

To solve this problem, we need to remember is that a square has four sides of equal length. This means that given one side length, we know all the other side lengths. The formula for perimeter is , which is the same thing as adding all the side lengths together.

or

4

What is the perimeter of the equilateral triangle below?

Screen shot 2015 11 09 at 8.59.58 am

Explanation

An equilateral triangle means that all of the side lengths are the same. To find the perimeter, we can take the one known side length and multiply by (since there are sides) or we can add the side length to itself times.

$9\times3=27$

5

What is the perimeter of the triangle below?

Screen shot 2015 11 09 at 8.17.56 am

Explanation

To find the perimeter, we add all of the side lengths together.

6

What is the perimeter of the polygon below?

Explanation

To find the area of a perimeter, we add all of the side lengths together.

7

What is the perimeter of the polygon below?

Explanation

To find the area of a perimeter, we add all of the side lengths together.

8

What is the perimeter of the square below?

Screen shot 2015 11 05 at 8.19.52 am

Explanation

To solve this problem, we need to remember is that a square has four sides of equal length. This means that given one side length, we know all the other side lengths. The formula for perimeter is , which is the same thing as adding all the side lengths together.

or

9

What is the perimeter of the square below?

Screen shot 2015 11 05 at 8.23.29 am

Explanation

To solve this problem, we need to remember is that a square has four sides of equal length. This means that given one side length, we know all the other side lengths. The formula for perimeter is , which is the same thing as adding all the side lengths together.