ForMuLas FoR GeoMeTry

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ForMuLas FoR GeoMeTry

  1. 1. Formulas for Geometry Mr. RyanVisit www.worldofteaching.com for more free powerpoints
  2. 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! 2 Free powerpoint template: www.brainybetty.com
  3. 3. Perimeter•Any shape’s “perimeter” is the outside of the shape…like a fence around a yard. 3 Free powerpoint template: www.brainybetty.com
  4. 4. Perimeter•To calculate the perimeter of any shape, just add up “each” line segment of the “fence”. 4 Free powerpoint template: www.brainybetty.com
  5. 5. Perimeter•Triangles have 3 sides…add up each sides length. 8 8 8+8+8=24 8 The Perimeter is 24 5 Free powerpoint template: www.brainybetty.com
  6. 6. Perimeter•A square has 4 sides of a fence 12 12 12 12+12+12+12=48 12 6 Free powerpoint template: www.brainybetty.com
  7. 7. Perimeter•Sometimes, problems may only give you two measurements for a square or rectangle.•No problem…use the formula for squares/rectangles (only!) 7 Free powerpoint template: www.brainybetty.com
  8. 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 8 Free powerpoint template: www.brainybetty.com
  9. 9. The Same!!•If the bottom is 15…the top is… 15 9 Free powerpoint template: www.brainybetty.com
  10. 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=8014 20 25 10 Free powerpoint template: www.brainybetty.com
  11. 11. Other shapes•Just add up EACH segment 10 8 sides, each side 10 so 10+10+10+10+10+10+10+10=80 11 Free powerpoint template: www.brainybetty.com
  12. 12. Odd shapes• Count ALL sides• Remember if one side blank, it’s equal to its opposite 25+25=50 (for Length) 15+5+15+5=40 (for Width) 5 15 Perimeter=90 25 12 Free powerpoint template: www.brainybetty.com
  13. 13. Area•Area is the ENTIRE INSIDE of a shape•It is always measured in “squares” (sq. inch, sq ft) 13 Free powerpoint template: www.brainybetty.com
  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 3 4 2 units (ft, in, m) 14 Free powerpoint template: www.brainybetty.com
  15. 15. Area of Squares/Rectangles•Length x Width=Area 2 Length(2) xWidth(2) = 4 square units 15 Free powerpoint template: www.brainybetty.com
  16. 16. Parallelogram Area•Same idea as squares & rectangles, but they change the words to Base (length:bottom of shape) and height (width) 16 Free powerpoint template: www.brainybetty.com
  17. 17. Parallelogram Area•Area=Base x Height•(Area=length x width) The diagonal line is NOT 5 the height!!! Height (width) 8 BASE (length) Base 8 x Height 5 = Area 40 17 Free powerpoint template: www.brainybetty.com
  18. 18. REAL formula for area ofsquares•Area= S^2•Area= Side x Side (side squared) (just a different way of saying length x width) Side one Side two 18 Free powerpoint template: www.brainybetty.com
  19. 19. Different Names/Same idea•Length x Width = Area•Side x Side = Area•Base x Height = Area 19 Free powerpoint template: www.brainybetty.com
  20. 20. 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 5 = Area 4 x 5 = 20 Base 20 Free powerpoint template: www.brainybetty.com
  21. 21. Area of a Circle•Pi= 3.14•Radius: from center (origin) of circle to ANY side•Area= pi x (Radius x Radius) 21 Free powerpoint template: www.brainybetty.com
  22. 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) If the radius is 5, then the diameter is 10 22 Free powerpoint template: www.brainybetty.com
  23. 23. 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 23 Free powerpoint template: www.brainybetty.com
  24. 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 24 Free powerpoint template: www.brainybetty.com
  25. 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. 25 Free powerpoint template: www.brainybetty.com

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