Formulas geometry
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  • 1. Formulas for Geometry
  • 2. 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
  • 3. Perimeter
    • Any shape ’ s “ perimeter ” is the outside of the shape…like a fence around a yard.
    Free powerpoint template: www.brainybetty.com
  • 4. Perimeter
    • To calculate the perimeter of any shape, just add up “ each ” line segment of the “ fence ” .
    Free powerpoint template: www.brainybetty.com
  • 5. Perimeter
    • Triangles have 3 sides…add up each sides length.
    Free powerpoint template: www.brainybetty.com 8 8 8 8+8+8=24 The Perimeter is 24
  • 6. Perimeter
    • A square has 4 sides of a fence
    Free powerpoint template: www.brainybetty.com 12 12 12 12 12+12+12+12=48
  • 7. 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
  • 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
    Free powerpoint template: www.brainybetty.com
  • 9. The Same!!
    • If the bottom is 15…the top is…
    Free powerpoint template: www.brainybetty.com 15
  • 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
    Free powerpoint template: www.brainybetty.com 14 25 20
  • 11. Other shapes
    • Just add up EACH segment
    Free powerpoint template: www.brainybetty.com 10 8 sides, each side 10 so 10+10+10+10+10+10+10+10=80
  • 12. Odd shapes
    • Count ALL sides
    • Remember if one side blank, it ’ s equal to its opposite
    Free powerpoint template: www.brainybetty.com 25 15 5 25+25=50 (for Length) 15+5+15+5=40 (for Width) Perimeter=90
  • 13. Area
    • Area is the ENTIRE INSIDE of a shape
    • It is always measured in “ squares ” (sq. inch, sq ft)
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  • 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)
    Free powerpoint template: www.brainybetty.com 1 2 units (ft, in, m) 2 3 4
  • 15. Area of Squares/Rectangles
    • Length x Width=Area
    Free powerpoint template: www.brainybetty.com 2 Length(2) xWidth(2) = 4 square units
  • 16. 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
  • 17. Parallelogram Area
    • Area=Base x Height
    • (Area=length x width)
    Free powerpoint template: www.brainybetty.com BASE (length) Height (width) 8 5 Base 8 x Height 5 = Area 40 The diagonal line is NOT the height!!!
  • 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)
    Free powerpoint template: www.brainybetty.com Side one Side two
  • 19. Different Names/Same idea
    • Length x Width = Area
    • Side x Side = Area
    • Base x Height = Area
    Free powerpoint template: www.brainybetty.com
  • 20. Area of a Triangle
    • ½ Base x Height = Area
    • (It ’ s ½ because ½ of the “ square ” is missing)
    Free powerpoint template: www.brainybetty.com Base Height Height Base 8 5 ½ Base x Height = Area ½ (8) x 5 = Area 4 x 5 = 20
  • 21. 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
  • 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 (It ’ s twice the radius)
    Free powerpoint template: www.brainybetty.com If the radius is 5, then the diameter is 10
  • 23. Area of a circle
    • Area = piR^2
    • Pi = 3.14 and R=Radius
    Free powerpoint template: www.brainybetty.com Radius 5 Area=3.14 x (5 x 5) Perimeter = 3.14 x 10
  • 24. 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
  • 25.
    • 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.
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