Formulas for geometry

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 sides length. 8 8 8 8+8+8=24 The Perimeter is 24 5 Free powerpoint template: www.brainybetty.com Perimeter •A square has 4 sides of a fence 12 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 25 Free powerpoint template: www.brainybetty.com 20 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 25+25=50 (for Length) 15+5+15+5=40 (for Width) 5 15 Perimeter=90 Free powerpoint template: www.brainybetty.com 12 25 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) 5 Height (width) The diagonal line is NOT the height!!! 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 length x width) Side one 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 the “square” is Height missing) 5 Base 8 Height ½ Base x Height = Area ½ (8) x 5 = Area 4 x 5 = 20 20 Base Free powerpoint template: www.brainybetty.com 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