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Lesson 1: Perimeter

# 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

Problem 1A
Each square on the grid is $1$ unit square.
What is the perimeter of the rectangle?
units

Problem 1B
Each square on the grid is $1$ unit square.
What is the perimeter of the square?
units

## Irregular shapes

Problem 2A
Each square on the grid is $1$ unit square.
What is the perimeter of the shape?
units

Problem 2B
Each square on the grid is $1$ unit square.
What is the perimeter of the shape?
units

## 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?
• 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
• you can get it on learning through the video or practicing some exercise
Good luck!!
• what if its a 3 dementinal circle how will you find the primiter?
• First you subtract the dementinal then you use the angels then you get the answer.
• Is there a way that you can find out the perimetre of a circle?
• Good question!

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.
• If its a round shape are you able to find the perimeter.
• 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"
• I can count the sides but it takes way to long so I just multiply. And add.
• how do you find perimeter of a square if you only have the volume of the square?
• 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