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### Course: Basic geometry and measurement>Unit 1

Lesson 6: Perimeter intro

# 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.
• that was super duper easy
• qwertyuiuytrewqqwertyuio
• Could you maybe make the shapes a little more creative?
• Does the area have anything to do with the perimeter?
• 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