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Geometry: Perimeter Formulas Rectangle: P = 2l + 2w Triangle: P=a+b+c Parallelogram: Square: P = 4s Trapezoid: P = c + b1 + b 2 + d P = 2c + 2b Regular shapes have sides with equal lengths. Find the perimeter: Rectangle Square Triangle 11 4 6 3 2 4 P = 2l + 2w P = 4s P = 2( 11 ) + 2( 4 ) P = 4( P = 22 + 8 P = 30 units ) 2 Find the perimeter: Trapezoid 7 5 4.5 Parallelogram 4 3 8 If two sides of an isosceles triangle are 6 in and the third side is 8 in, find the perimeter. The length of a rectangular park is 55 yd. The width is 47 yd. How many yards of fencing are needed to surround the park? 3 Geometry: Area & Circles Formulas Rectangle: P = 2l + 2w A = lw Triangle: P=a+b+c A = ½ bh Parallelogram: Square: P = 4s A = s2 Trapezoid: P = c + b1 + b 2 + d A = ½ (b1 + b2)h P = 2c + 2b A = bh Find the Area. 14 ft 5 c m 9 cm 6 ft 7 1/3 in A = lw A = s2 A = ( 14 )( 6 ) A=( A= )2 A = 84 sq. ft 11 yd 2 6.4 yd m 4m 15.3 yd A= A= 4 The height of a trapezoid is 5 in. The base measures 16 in. and 18 in. Find the area of the trapezoid. The length of the base of a parallelogram is 6 ½ in. and the height is 10 ¼ in. Find the area of the parallelogram. 5 Circles: Circumference & Area The diameter, which goes through the center of the circle, is twice the length of the radius. Circumference is the distance around the “edge” of the circle. C = 2πr Circumference is very similar to perimeter. Area is all the “space” inside the circle. A = π r2 π is a Greek letter pronounced as pie, and is an irrational number (there is no end to the numbers behind the decimal and no pattern to those numbers). 22 We use numbers like 3.14 and as an approximation for to calculate answers. 7 π Radius The length from the center to the edge of the circle. Circumference Diameter The length from one edge of the circle to the opposite edge through the center. Area 6 Find the Circumference and Area of each circle. 5 3.4 ft 2 C = 2πr C = 2 ( 3.14 )( 5 ) C = 31. 4 units A = π r2 A = ( 3. 14)( 5 )2 A = ( 3.14 )(25) A = 78.5 sq units 6 m 11