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### Course: 3rd grade > Unit 11

Lesson 1: Perimeter- Perimeter: introduction
- Perimeter of a shape
- Find perimeter by counting unit squares
- Find perimeter by counting units
- Finding perimeter when a side length is missing
- Find perimeter when given side lengths
- Finding missing side length when given perimeter
- Perimeter review

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# Perimeter review

Review the basics of perimeter and try some practice problems.

## What is perimeter?

Perimeter is the distance around the outside of a two-dimensional shape.

The perimeter of the shapes below is shown in ${\text{blue}}$ .

*Want to learn more about the concept of perimeter? Check out this video.*

## How do we calculate the perimeter of a shape?

To find the perimeter of a shape, we add all of the shape's side lengths.

### Example 1:

**What is the perimeter of the trapezoid?**

We can find the perimeter by adding all of the side lengths.

### Example 2:

**What is the perimeter of the regular pentagon?**

We can find the perimeter by adding all of the side lengths.

All sides of a

*regular*pentagon are the same length.*Want to learn more about calculating perimeter? Check out this video.*

## Practice set 1: Calculate perimeter

*Want to try more problems like this? Check out these exercises:*

Find perimeter when given side lengths

Find perimeter by counting unit squares

## Practice set 2: Challenge items

*Want to try more problems like this? Check out these exercises:*

Find a missing side length when given perimeter

Perimeter word problems

## Want to join the conversation?

- If two or more sides of a shape is unknown, what can you do to figure that out?(61 votes)
- If you want to figure it you have to see the othr stuff first then you would figure it out but if not i don't know it worked for me(12 votes)

- How will I use this in real life?(29 votes)
- So you will use it if you are going to build a house it will also help with fences!(2 votes)

- what is 100x10,000000?(8 votes)
- A certain number.(14 votes)

- its a bit challenging though. you really need analyzing skills for it ahaha.(11 votes)
- I love this so fun it is so fantastic(11 votes)
- Why do you put this here why why!(2 votes)

- how can you see perimeter in 3D polygons(13 votes)
- If two or more sides of a shape is unknown, what can you do to figure that out?(5 votes)
- Well, it depends on the shape, really...(5 votes)

- Yeah, I agree, Mr. Taylor—I got confused, the angle change puzzled me, but I realized my mistake and corrected it.(10 votes)