area and perimeter - 3rd grade australian math...

Area and Perimeter

Day 1

Problem of the Day

Brandon and his friends built a clubhouse that was 10 feet long and

8 feet wide. Later on, they decided to add a room that was 6 feet

long and 5 feet wide. Draw a picture of the clubhouse, and find

the total area.

Review

What is area?

What is perimeter?

How do you find the area of a shape?

How do you find the perimeter of a shape?

Rectilinear Figures

What is a rectilinear figure?

How do you find the area of a rectilinear figure?

Using graph paper is often the easiest way, but what if the shape is

too big for graph paper? What if we don’t have graph paper?

What if we want to do it a quicker way?

Rectilinear Figures

To find the area without using graph paper, you can split the

rectilinear figure into rectangles. After you split it, find the area of

each rectangle, then combine them to find the total area.

IMPORTANT REMINDER: If you split one of the sides, you need to

find the new lengths of each piece. How can you do that?

Helpful Hint: When I draw my dividing line, I like to make it extend

through the side so I remember that I need to split that side.

Rectilinear Figures

Let’s find the area of this shape:

How can we split up this shape to

find the area?

Which side will be split?

How do we find the new lengths of

that side?

Guided Practice

With your team, find the area of this shape:

Try On Your Own

Find the area of this shape on your own:

Independent Practice/ Centers

Complete the area worksheet for independent practice. When you

are finished, go to your center for the day.

Computer: Khan Academy 3rd grade mission

I Can: Area and Perimeter

I-pods: Multiplication Fluency

Partner Work: Create a rectilinear figure with given side lengths. Switch with your partner and find the area.

Area and Perimeter

Day 2

Problem of the Day

Mr. Moss has been looking at sketches for a new playground. The sketch of the playground he wants to build is in a rectilinear shape, to the right. There are 8 sides to the playground sketch. The side lengths of the rectilinear shape are 8 yd., 10 yd., 10 yd., 5 yd., 5 yd., 3 yd., 3yd., and 2 yd. Using the figure, correctly label the playground sketch Mr. Moss is interested in and then find the area of the shape.

Rectilinear Figures Review

What is a rectilinear figure?

• Polygon, or closed figure, that has all right angles

How do you find the area of a rectilinear figure?

• Use graph paper to count the squares, or

• Separate the shapes of the rectilinear figure, calculate the area of each of

the separated shapes, then find the sum for the areas of both separated

shapes

Rectilinear Figures

Let’s find the area of this shape:

How do we find the missing side

lengths?

What is the area of the large square?

What is the area of the small square?

What is the total area?

Rectilinear FiguresLet’s find the area of this shape:

How can we split up this shape to find the

area?

How do we find the missing side length?

What is the area of the large rectangle?

What is the area of the small rectangle?


Rectilinear FiguresLet’s find the area of this shape:

How can we split up this shape to find the

area?

How do we find the missing side lengths?

What is the area of the large rectangle?

What is the area of the small rectangle?


Guided Practice

With your team, find

the area of this shape:

Try On Your Own

Find the area of this

shape on your own:

Connecting it all

Today we reviewed what a rectilinear shape is and how to find the

area of a rectilinear shape with missing side length(s). Tomorrow

we will continue to work with rectilinear shapes by using the

distributive property to help us find the its area.


Complete the “Finding Area of Rectilinear Shapes” activity sheet for

independent practice. When you are finished, go to your center for the day.





Area and Perimeter

Day 3

Problem of the Day

A rectilinear figure has an an area of 20 and an area 16. Draw this figure and find the perimeter.

Rectilinear Figures Review

The Distributive Property breaks the rectilinear figure into multiple rectangles.

See the example on the next slide. We are basically doing the same thing that

we have been, but we are adding in one step to make it more clearly defined.

Rectilinear Figures

Using the Distributive Property, we

would set up the problem like this.

(5 x 4) + (2 x 2) = ?

20 + 4 = 24

Rectilinear Figures1. Find the missing side.

2. Divide the rectilinear figure into

multiple rectangles.

3. Use the Distributive Property to set up

the problem.

Rectilinear Figures1. Find the missing side.

2. Divide the rectilinear figure into

multiple rectangles.

3. Use the Distributive Property to set

up the problem.

Guided Practice

With your team, find

the area of this shape,

using the distributive

property:

Try On Your Own


shape on your own,

using the distributive

property:

Try On Your Own


shape on your own,

using the

distributive

property:


Complete the “Finding Area of Rectilinear Shapes” activity sheet for

independent practice. When you are finished, go to your center for the day.





Area and Perimeter

Day 4

Problem of the Day

Mr. Maxwell built a clubhouse for his children that has a

length of 5 feet and an area of 55 square feet. What is the

width of his clubhouse?

Word Problems with Rectilinear Figures

Today, we will be solving area and perimeter word problems.

Make sure to read the word problem carefully!

How can you decide whether you are solving for area or

perimeter if the problem doesn’t specifically say?

Guided Practice

Ms. Klinger wants to build a pool in her backyard. She made a drawing

of what she wants it to look like, but she needs to know the total area that

the pool will take up before it can be built. What is the total area of her

pool?

Guided Practice

The PTA installed a new jungle gym on the playground. They

need to put a border around the playground. How much border

should they buy?

Try On Your Own

Jamiah planted a garden like the one below. She wanted to put a

fence around it to keep animals out. How much fencing does she

need?

Try On Your Own

Billy is redecorating his bedroom and would like to replace the

carpet. His square room has a perimeter of 24 inches. What is the

amount of carpet he will need to cover the floor of his bedroom?


Complete the area worksheet for independent practice. When you

are finished, go to your center for the day.





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