# Formulas for Geometry Mr. Ryan

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Formulas for Geometry Mr. Ryan
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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:

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Perimeter Any shape’s “perimeter” is the outside of the shape…like a fence around a yard. Free powerpoint template:

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Perimeter To calculate the perimeter of any shape, just add up “each” line segment of the “fence”. Free powerpoint template:

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Perimeter Triangles have 3 sides…add up each sides length. 8 8 8+8+8=24 The Perimeter is 24 8 Free powerpoint template:

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Perimeter A square has 4 sides of a fence 12 12 12 =48 12 Free powerpoint template:

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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:

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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:

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The Same!! If the bottom is 15…the top is… 15 Free powerpoint template:

Square/Rectangle Formula
Perimeter=2(Length+Width) P= 2(25+14) P=2(20+20) P= P=40+40 P= P=80 14 20 25 Free powerpoint template:

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Other shapes Just add up EACH segment 10 8 sides, each side 10 so =80 Free powerpoint template:

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Odd shapes Count ALL sides Remember if one side blank, it’s equal to its opposite =40 (for Width) 25+25=50 (for Length) 5 15 Perimeter=90 25 Free powerpoint template:

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Area Area is the ENTIRE INSIDE of a shape It is always measured in “squares” (sq. inch, sq ft) Free powerpoint template:

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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:

Area of Squares/Rectangles
Length x Width=Area 2 Length(2) xWidth(2) = 4 square units Free powerpoint template:

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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) Free powerpoint template:

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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:

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 Free powerpoint template:

Different Names/Same idea
Length x Width = Area Side x Side = Area Base x Height = Area Free powerpoint template:

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Area of a Triangle ½ Base x Height = Area (It’s ½ because ½ of the “square” is missing) Height 5 Base 8 Height ½ Base x Height = Area ½ (8) x = Area x = 20 Base Free powerpoint template:

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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:

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:

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Area of a circle Area = piR^2 Pi = and R=Radius 5 Radius Area=3.14 x (5 x 5) Perimeter = 3.14 x 10 Free powerpoint template:

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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:

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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: