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Basic Geometry Perimeter & Circumference. Tallaney Nilson. Perimeter. Perimeter of a polygon is the distance around it. 75yrds. 100yrds. 150 yds. 100yrds. 75yrds. 75 + 150 + 100 + 100 + 75 = 150. Formula’s. Triangle
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Basic Geometry Perimeter & Circumference Tallaney Nilson
Perimeter Perimeter of a polygon is the distance around it. 75yrds 100yrds 150 yds 100yrds 75yrds 75 + 150 + 100 + 100 + 75 = 150
Formula’s Triangle P= a + b + c Perimeter equals the sum of the length of the three sides. Example A = 12 cm B = 20 cm C = 24 cm P = 12 + 20 +24 P = 56 cm
Formula’s Rectangle P= 2L = 2w Perimeter equals twice the length plus twice the width. Example L = 10 m P = 2 * 10 + 2.5 = 20 + 10 = 30 m W = 5 m
Formula’s Square P = 4s Perimeter equals four times the length of a side. Example P = 4 * 6 = 24 ft S = 6 ft
Circumference of a Circle The distance around a circle is called its circumference. Diameter ( d ) Circumference ( c ) Radius ( r) c/d = pie C = pie(d) C = 2pie( r)
Example 4 m Solutions The radius of the circle is 4 m. W use the formula for the circumference of a circle in terms of the radius. c = 2pie( r ) = 2(3.14)(4) = 25.12m Therefore the circumference is 25.12 m
Composite figures Composite figures are two or more basic figures that can be combined. Example 5 ft Find the perimeter of this figure, which consists of a semicircle and a rectangle. 7 ft Solution The top of the figure is a semicircle with a diameter of 7 ft. Distance around the semicircle is 1/ 2 the circumference of the entire circle. C = pie(d) ~ 22/7(7) ~ 22 or 11ft
Composite figure Now we need to find the perimeter of three sides of the rectangle at the bottom of the figure. P = 5 +7 + 5 = 17 Total Perimeter = Circumference of top + Perimeter of bottom = 11 ft + 17 ft = 28 ft
Problem Solution >we want to find the perimeter of the building. So we break the composite figure into three basic shapes> two rectangles and one square. 170 115 115 170 170 We find the length Of the indented part of Each rectangular shape By subtracting 170 ft From 210 ft to get 40 ft. 210 210 170 40 40 115 115 P = (115 + 210 + 115 + 40) + (170 + 170) + (115 + 210 + 115 + 40) P = 1,300 ft