# Formulas for GeometryPage 2

13

## Area

Area is the ENTIRE INSIDE of a shape

It is always measured in “squares” (sq. inch, sq ft)

Slide 14 14

AREA

Square units means that “that” many squares fit inside that shape (if measured in feet…it’s feet…if meters…it’s meters. In this example the area is 4 square units…note 4 squares fit)

1

2 units (ft, in, m)

2

3

4

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## Area of Squares/Rectangles

Length x Width=Area

2

Length(2) xWidth(2) = 4 square units

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## Parallelogram Area

Same idea as squares & rectangles, but they change the words to Base (length:bottom of shape) and height (width)

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Parallelogram Area

Area=Base x Height

(Area=length x width)

BASE (length)

Height (width)

8

5

Base 8 x Height 5 = Area 40

The diagonal line is NOT

the height!!!

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## Real formula for area of squares

Area= S^2

Area= Side x Side (side squared) (just a different way of saying length x width)

Side one

Side two

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## Different Names/Same idea

Length x Width = Area

Side x Side = Area

Base x Height = Area

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## Area of a Triangle

½ Base x Height = Area

(It’s ½ because ½ of the “square” is missing)

Base

Height

Height

Base

8

5

½ Base x Height = Area

½ (8) x 5 = Area

4 x 5 = 20

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## Area of a Circle

Pi= 3.14

Radius: from center (origin) of circle to ANY side

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## Circumference of a Circle

Perimeter/Circumference = pi x diameter

Pi is always 3.14

Circumference is a fancy name for perimeter

The diameter is a line from one side to the other side of a circle through its origin (It’s twice the radius)

If the radius is 5, then the diameter is 10

Slide 23 23

Area of a circle

Area = piR^2

5

Area=3.14 x (5 x 5)

Perimeter = 3.14 x 10

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