Find the area and circumference of each circle

Find the area and circumference of each circle. Leave answers in terms of π. C=2 • π • r , A = π • r 2 1) 4 m 2) 3) r = 9 cm d = 12 in C=2 • π • 4 m = 8π m A = π • (4 m)2 = 16π m 2 C = 2 • π • 9 cm = 18π cm A = π • (9 cm)2 = 81π cm 2 C = 2 • π • 6 in = 12π in A = π • (6 in)2 = 36π in 2

18. 06 Area & Perimeter of Irregular Figures

Recall: Area Formulas Rectangle: A = b • h Parallelogram: A = b • h Triangle: A = ½ • b • h Trapezoid: A = ½ • h • (b 1 + b 2) Circle: A = π • r 2 Recall: Perimeter is defined as the distance around the figure, adding up the lengths of the sides. Rectangle: P = 2 b + 2 h Circle: C = 2 • π • r

Some figures are a composition of two or more figures. This type of figure is called a compound polygon. Examples: To find the area , divide the figure up into smaller pieces and use the formulas to find each area and combine them.

Find the perimeter and area. 7 2 2 10 8 To find the perimeter, find the two missing sides. P = 7 + 10 + 5 + 8 + 2 = 34 5 To find the area, find the area of the 2 rectangles. The area of the top rectangle is 7 • 2 = 14 The area of the bottom rectangle is 5 • 8 = 40 The area of the figure is 14 + 40 = 54

Find the perimeter and area. 15 7 6 9 To find the perimeter, find the missing side. P = 12 + 7 + 9 + 15 + 7 7 = 50 12 To find the area, find the area of the triangle and parallelogram. The area of the triangle is ½ • 12 • 9 = 54 The area of the parallelogram is 12 • 6 The area of the figure is 54 + 72 = 126 = 72