Main content

### Course: 3rd grade (Eureka Math/EngageNY) > Unit 7

Lesson 3: Topic C: Problem solving with 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
- Find a missing side length when given perimeter
- Find perimeter when a side length is missing
- Perimeter word problem: skating rink
- Perimeter word problem: tables
- Perimeter word problems
- Perimeter review

© 2024 Khan AcademyTerms of usePrivacy PolicyCookie Notice

# Find perimeter by counting unit squares

Practice finding perimeter by counting unit squares. We will start with rectangles and then try some irregular shapes.

## Rectangles

## Irregular shapes

## Want to join the conversation?

- if it is a round shape , can you find the perimeter or not? if yes how do you find it?(143 votes)
- Well you can get a perimeter but it is easy cause there is no adding. ⭕ this is a circle so you can find the perimeter cause the out side border. also in a cirle it is not called perimeter it is called circumference(85 votes)

- why do you get energy points(30 votes)
- you can get it on learning through the video or practicing some exercise

Good luck!!(24 votes)

- what if its a 3 dementinal circle how will you find the primiter?(21 votes)
- First you subtract the dementinal then you use the angels then you get the answer.(28 votes)

- Is there a way that you can find out the perimetre of a circle?(19 votes)
- Good question!

The answer is yes.

First, we need to talk about a special number called pi. Pi is the unending, non-repeating decimal 3.1415926535897... . Common approximations used for pi are 3.14 and 22/7.

Second, we need to talk about diameter and radius of a circle. A diameter is a segment that connects two points on a circle and passes through the center. The radius is a segment that connects the center and a point on a circle. We call the length of any diameter "the diameter", and the length of any radius "the radius". The diameter is always twice the radius.

Finally, the perimeter, or**circumference**, of a circle is equal to pi times the diameter. The circumference is also equal to 2 times pi times the radius. This means that the circumference of a circle is a little more than 3 times its diameter, and is a little more than 6 times its radius.(26 votes)

- If its a round shape are you able to find the perimeter.(18 votes)
- As Lisa Eeyore said (in the comments) "Yes, it's called the circumference. If you know the radius, you can calculate the circumference which is 2 x pi x radius"(12 votes)

- I can count the sides but it takes way to long so I just multiply. And add.(20 votes)
- Could you maybe make the shapes a little more creative?(20 votes)
- that was super duper easy(19 votes)
- qwertyuiuytrewqqwertyuio(2 votes)

- Does the area have anything to do with the perimeter?(14 votes)
- Hello, Mabel!

The area and the perimeter of shapes don't have too much in common, aside from the fact that the length and width of the shape must be known to find both. Perimeter of a rectangle can be written as*P=(2*L)+(2*W)*, while area is*A=L*W*(11 votes)

- how do you find perimeter of a square if you only have the volume of the square?(11 votes)
- You do not find the volume of a square you find the area. In order to find the perimeter of a square from the area find what number multiplied by itself gives you the area of the square. then you multiply that number by 4 to get the perimeter because all sides of a square are the same length.

For example

a square with the area of 36 square units

6x6=36

so each side of the square is 6 units because to find the area you multiply the length by the height and since all sides of a square are the same, length=height

then you find the perimeter of a by multiplying the length by 4 or add all the side together

6x4=24

6+6+6+6=24

the perimeter = 24 units(15 votes)