Transcript Formulas for Geometry Mr. Ryan Visit www.worldofteaching.com for more free powerpoints Don’t Get Scared!!! •Evil mathematicians have created formulas to save you time.

Formulas for
Geometry
Mr. Ryan
Visit www.worldofteaching.com for more free powerpoints
Don’t Get Scared!!!
•Evil mathematicians
have created formulas
to save you time. But,
they always change the
letters of the
formulas to scare you!
Free powerpoint template: www.brainybetty.com
2
Perimeter
•Any shape’s “perimeter”
is the outside of the
shape…like a fence
around a yard.
Free powerpoint template: www.brainybetty.com
3
Perimeter
•To calculate the
perimeter of any shape,
just add up “each” line
segment of the “fence”.
Free powerpoint template: www.brainybetty.com
4
Perimeter
•Triangles have 3
sides…add up each side’s
length.
8
8
8
8+8+8=24
The Perimeter is 24
Free powerpoint template: www.brainybetty.com
5
Perimeter
•A square has 4 sides of
12
a fence
12
12
12+12+12+12=48
12
Free powerpoint template: www.brainybetty.com
6
Perimeter
•Sometimes, problems may
only give you two
measurements for a
square or rectangle.
•No problem…use the
formula for
squares/rectangles
(only!)
Free powerpoint template: www.brainybetty.com
7
Remember
• Squares - ALL sides are
equal…so if they give you one
side, you know ALL the sides
• Length=the Largest side
• If they “leave” numbers out, they
are equal to their opposite side.
If they give you the bottom of a
square/rectangle type shape
then the top is the same
Free powerpoint template: www.brainybetty.com
8
The Same!!
•If the bottom is 15…the
top is…
15
Free powerpoint template: www.brainybetty.com
9
Square/Rectangle
Formula
• Perimeter=2(Length+Width)
• P= 2(25+14)
P=2(20+20)
• P= 50+28
P=40+40
• P= 78
P=80
14
20
25
Free powerpoint template: www.brainybetty.com
10
Other shapes
•Just add up EACH
segment
10
8 sides, each side 10 so 10+10+10+10+10+10+10+10=80
Free powerpoint template: www.brainybetty.com
11
Odd shapes
• Count ALL sides
• Remember if one side blank, it’s equal to its
opposite
15+5+15+5=40 (for Width)
25+25=50 (for Length)
5
15
25
Perimeter=90
Free powerpoint template: www.brainybetty.com
12
Area
•Area is the ENTIRE
INSIDE of a shape
•It is always measured in
“squares” (sq. inch, sq
ft)
Free powerpoint template: www.brainybetty.com
13
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
3
4
2 units (ft, in, m)
Free powerpoint template: www.brainybetty.com
14
Area of
Squares/Rectangles
•Length x Width=Area
2
Length(2) xWidth(2) = 4 square units
Free powerpoint template: www.brainybetty.com
15
Parallelogram Area
•Same idea as squares &
rectangles, but they
change the words to
Base (length:bottom of
shape) and height
(width)
Free powerpoint template: www.brainybetty.com
16
Parallelogram Area
•Area=Base x Height
•(Area=length x width)
The diagonal line is NOT
the height!!!
5
Height (width)
8
BASE (length)
Base 8 x Height 5 = Area 40
Free powerpoint template: www.brainybetty.com
17
REAL formula for area
of squares
•Area= S^2
•Area= Side x Side (side
squared) (just a
different way of saying
lengthSidexonewidth)
Side two
Free powerpoint template: www.brainybetty.com
18
Different Names/Same
idea
•Length x Width = Area
•Side x Side = Area
•Base x Height = Area
Free powerpoint template: www.brainybetty.com
19
Area of a Triangle
•½ Base x Height = Area
•(It’s ½ because ½ of
Height
the “square” is missing)
5
Base
8
Height
Base
½ Base x Height = Area
½ (8) x 5 = Area
4
x
5 = 20
Free powerpoint template: www.brainybetty.com
20
Area of a Circle
•Pi= 3.14
•Radius: from center
(origin) of circle to
ANY side
•Area= pi x (Radius x
Radius)
Free powerpoint template: www.brainybetty.com
21
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
Free powerpoint template: www.brainybetty.com
22
Area of a circle
•Area = piR^2
•Pi = 3.14 and R=Radius
5
Radius
Area=3.14 x (5 x 5)
Perimeter = 3.14 x 10
Free powerpoint template: www.brainybetty.com
23
You’re Done
•Squares, rectangles and
parallelograms area are
almost the same (LxW)
•Triangles are ½ cause
your missing ½
•Circles have fancy names,
but just follow the
formula
Free powerpoint template: www.brainybetty.com
24

•For most tests you will
have the formulas given
to you. Just remember
which one to use for
which shape and you’ll
do fine.
Free powerpoint template: www.brainybetty.com
25