Area and Perimeter of Polygons

Area of Polygons

Last class...

We learned that we can compose/decompose shapes from other shapes. Specifically, we looked at squares, rectangles, and triangles.

Squares can be formed from...

Two triangles!

Multiple Choice

What is the area of a square with sides measuring 4in?

• 8

• 12

• 16

• 24

Since a triangle is half of a square/rectangle...

We treat it as such!

Multiple Choice

What is the area of one TRIANGLE if the SQUARE'S area is 16in?

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But what about other shapes?

Let's explore and decompose some shapes!

But quick. Here's a meme.

This is a hexagon. It has six sides.

Let's decompose this hexagon!

It's not just a hexagon...

They're six triangles!

Poll

Can you think of another way to decompose this hexagon?

• Yes.

• Yes!!

• Y E S S S

• Y

Now we have one rectangle, and two triangles!

Can we decompose this parallelogram?

Poll

What shapes are you able to decompose it to?

• Rectangle

• Triangles

• Circles

Great job!

Have a meme.

Let's look at real life examples!

Here's a house.

Here's a house on math.

Here's a simplified house on math.

Notice that this irregular shape (called a compound shape) can be decomposed to a triangle and a square.

In the next slide, I'll ask for the area of the triangle.

Multiple Choice

What is the area of the triangle?

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In the next slide, I'll ask for the area of the square.

Multiple Choice

What is the area of the square?

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The total area is 57ft.

How?

Great job! Here's another meme.

Follow up meme.

Let's do another one!

Let's decompose this compound shape!

Multiple Choice

Which is the proper way to decompose this compound shape?

• Hey wait, that's a trick question. They both can be right!

Yep! Let's look at this one for now.

In the next slide, you'll be asked to find the area of the orange rectangle.

Multiple Choice

What's the area of the orange rectangle?

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What about the green rectangle?

Multiple Choice

What's the area of the green rectangle?

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• 50

• 55