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Formulas for Geometry Mr. Ryan Visit www.worldofteaching.com for more free powerpointswww.worldofteaching.com

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Free powerpoint template: www.brainybetty.com 2 Dont Get Scared!!! Evil mathematicians have created formulas to save you time. But, they always change the letters of the formulas to scare you!

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Free powerpoint template: www.brainybetty.com 3 Perimeter Any shapes perimeter is the outside of the shape…like a fence around a yard.

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Free powerpoint template: www.brainybetty.com 4 Perimeter To calculate the perimeter of any shape, just add up each line segment of the fence.

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Free powerpoint template: www.brainybetty.com 5 Perimeter Triangles have 3 sides…add up each sides length. 8 8 8 8+8+8=24 The Perimeter is 24

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Free powerpoint template: www.brainybetty.com 6 Perimeter A square has 4 sides of a fence 12 12+12+12+12=48

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Free powerpoint template: www.brainybetty.com 7 Perimeter Sometimes, problems may only give you two measurements for a square or rectangle. No problem…use the formula for squares/rectangles (only!)

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Free powerpoint template: www.brainybetty.com 8 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

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Free powerpoint template: www.brainybetty.com 9 The Same!! If the bottom is 15…the top is… 15

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Free powerpoint template: www.brainybetty.com 10 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 25 20

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Free powerpoint template: www.brainybetty.com 11 Other shapes Just add up EACH segment 10 8 sides, each side 10 so 10+10+10+10+10+10+10+10=80

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Free powerpoint template: www.brainybetty.com 12 Odd shapes Count ALL sides Remember if one side blank, its equal to its opposite 25 15 5 25+25=50 (for Length) 15+5+15+5=40 (for Width) Perimeter=90

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Free powerpoint template: www.brainybetty.com 13 Area Area is the ENTIRE INSIDE of a shape It is always measured in squares (sq. inch, sq ft)

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Free powerpoint template: www.brainybetty.com 14 AREA Square units means that that many squares fit inside that shape (if measured in feet…its feet…if meters…its 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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Free powerpoint template: www.brainybetty.com 15 Area of Squares/Rectangles Length x Width=Area 2 Length(2) xWidth(2) = 4 square units

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Free powerpoint template: www.brainybetty.com 16 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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Free powerpoint template: www.brainybetty.com 17 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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Free powerpoint template: www.brainybetty.com 18 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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Free powerpoint template: www.brainybetty.com 19 Different Names/Same idea Length x Width = Area Side x Side = Area Base x Height = Area

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Free powerpoint template: www.brainybetty.com 20 Area of a Triangle ½ Base x Height = Area (Its ½ because ½ of the square is missing) Base Height Base 8 5 ½ Base x Height = Area ½ (8) x 5 = Area 4 x 5 = 20

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Free powerpoint template: www.brainybetty.com 21 Area of a Circle Pi= 3.14 Radius: from center (origin) of circle to ANY side Area= pi x (Radius x Radius)

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Free powerpoint template: www.brainybetty.com 22 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 (Its twice the radius) If the radius is 5, then the diameter is 10

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Free powerpoint template: www.brainybetty.com 23 Area of a circle Area = piR^2 Pi = 3.14 and R=Radius Radius 5 Area=3.14 x (5 x 5) Perimeter = 3.14 x 10

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Free powerpoint template: www.brainybetty.com 24 Youre 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

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Free powerpoint template: www.brainybetty.com 25 For most tests you will have the formulas given to you. Just remember which one to use for which shape and youll do fine.

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