Which of the following areas are you trying to find?

Parallelogram Triangle Trapezoid

AREAS OF POLYGONS

AREA OF A PARALLELOGRAM

Welcome. Today you’re going to discover the formula for area of a parallelogram.

h

b

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AREA OF A PARALLELOGRAM

To do this let’s cut the left triangle and…

h

b

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slide it…

AREA OF A PARALLELOGRAM

h

h b

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slide it…

AREA OF A PARALLELOGRAM

h

h

b

slide it…

AREA OF A PARALLELOGRAM

h

h

b

slide it…

AREA OF A PARALLELOGRAM

h

hb

…thus, changing it to a rectangle.

What is the area of the rectangle?

AREA OF PARALLELOGRAM

h

b

bhA hbA bhA 2

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You Answered Correctly.

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AREA OF A PARALLELOGRAM

Since the area of the rectangle and parallelogram are the same, just rearranged, what is the formula for the

area of this parallelogram?

h

b

bhA hbA bhA 2

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You Answered Correctly.

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The next slide will take you into discovering the

area of a triangle.

Do you wish to continue?

Yes No

AREA OF A TRIANGLE

Hello. You will now be discovering the formula for area of a triangle.h

bClick to Continue

AREA OF A TRIANGLE

Let’s divide the triangle so that we divide the

height in two.

b

?

?

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AREA OF A TRIANGLE

Now take the top and rotate…

b

?

?

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Remember, we divided the height into two equal

parts.

AREA OF A TRIANGLE

rotate…

?

?

AREA OF A TRIANGLE

?

?

b

rotate…

AREA OF A TRIANGLE

?

?

b

rotate…

AREA OF A TRIANGLE

?

?

b

rotate…

AREA OF A TRIANGLE

?

?

b

rotate…

AREA OF A TRIANGLE

??

b

…until you have a parallelogram.

How would you represent the height of this parallelogram?

h2 h21h

AREA OF A TRIANGLE

??

b

b

?

?

Remember, you divided the height in two.

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AREA OF A TRIANGLE

?

b

What is the area of this parallelogram?

bhA hbA 21 bhA 2

Congratulations!!!

You Answered Correctly.

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AREA OF A TRIANGLE

The area of this triangle would be the same as the parallelogram. Therefore, the formula for the area of a triangle is… what?h

b

bhA hbA 21 bhA 2

Congratulations!!!

You Answered Correctly.

Click to continue.