Perimeter and Area of Rectangles

Perimeter and
Area of Rectangles

What is Perimeter?

- Think of perimeter like a fence. How long of a fence do you need to go around the rectangle?

Let's say that each square is 1 unit long and 1 unit wide.

Multiple Choice

Count the units along the edges to see how long

of a fence you'd need to go around this rectangle.

• 15

• 16

• 12

• 10

Finding Perimeter by Multiplying

- You can also find the perimeter of a rectangle by noticing that the opposite sides are equal. So you could just figure out the length and the height, and double them.

- Each row has 5 units wide and 3 units long. So the perimeter is 2(L+W).


In our example, let's figure out the perimeter together using this formula.

Multiple Choice

Using the formula P = 2(W+L), find the perimeter of this rectangle.

• 14 units

• 13 units

• 15 units

• 1,000 units

What is Area?

- Area is the amount of space taken up by a two-dimensional shape.

- You can measure the area of a shape by counting how many unit squares fit within it.

- A unit square has an area of one square unit.

Multiple Choice

What is the area of this rectangle?

• 12

• 10

• 15

• 14

Why is the area 15?

- This rectangle is covered by 15 unit squares.

- So, the area of the rectangle is 15 square units

Finding Area by Multiplying

- You can also find the area of a rectangle by multiplying.

- Each row has 5 unit squares. There are 3 rows of unit squares.

- You can multiply the Length and the Width to find the area.

Multiple Choice

Which equation will help you find the area?

• 5 x 3

• 5 + 5 + 3 + 3

• 3 + 5

• 5 + 3

Area Formula

Length: How long an object is.

Width: The measurement of the side of an object that is normally the shorter side.

If you have the width and the length of a rectangle you can multiply them to get the area

Multiple Choice

Find the area of the rectangle.

• Area = 13

• Area = 26

• Area = 42

• Area = 49

How to find the area

- Multiply the length by the width.

- The length is 7 and the width is 6.

- So, 7 x 6 = 42

- Your area is 42 square units

Open Ended

What are two things you learned in this lesson?

Poll

How confident do you feel about area and perimeter of a rectangle?

• 😫

• 🤔

• 😐

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