CIRCUMFERENCE AND AREA OF CIRCLES LESSON 21

LETS REVIEW Perimeter of a Square P = 4s Area of a Square A= s2 Perimeter of a Rectangle P = 2L + 2W Area of a Rectangle A= LW or Bh

LETS REVIEW bh 2 A = Perimeter of a Parallelogram P = 2b + 2s Area of a Parallelogram A= bh Perimeter of a Triangle P = s + s + s bh 2 Area of a Triangle A =

LETS REVIEW h(a+b) 2 A= Perimeter of a Trapezoid P = s + s + s + s Area of a Trapezoid A=

EXAMPLE 1 Circumference of a Circle Area of a Circle Find the circumference and area of the figure. Circumference of a Circle C = 3.14(10) C = 31.4 cm Area of a Circle A = 3.14(5)2 A = 3.14(25) A = 78.5 cm2 Radius is half the diameter

YOU TRY! Find the circumference and area of the figure. 3 mm

SOLUTION Circumference of a Circle Area of a Circle Find the circumference and area of the figure. Circumference of a Circle C = 3.14(6) C = 18.84 mm 3 mm Area of a Circle A = 3.14(3)2 A = 3.14(9) A = 28.26 mm2 Diameter is twice the radius

EXAMPLE 2 Area of Big Circle Area of a Small Circle Find the area of the shaded figure. Area of Big Circle A = 3.14(10)2 A = 3.14(100) A = 314 cm2 Area of a Small Circle Area of Shaded Region Big Circle - Small Circle 314 - 50.24 263.76 cm2 A = 3.14(4)2 A = 3.14(16) A = 50.24 cm2

YOU TRY! Area of Big Circle Area of a Small Circle Find the area of the shaded figure. Area of Big Circle Area of a Small Circle Area of Shaded Region

SOLUTION Area of Big Circle Area of a Small Circle Find the area of the shaded figure. Area of Big Circle A = 3.14(5)2 A = 3.14(25) A = 78.5 mm2 Area of a Small Circle Area of Shaded Region Big Circle - Small Circle 78.5 - 12.56 65.94 mm2 A = 3.14(2)2 A = 3.14(4) A = 12.56 mm2

Class work Check solutions to Lesson 20 Copy notes and examples to Lesson 21 Do Lesson 21 worksheet