Circumference and area of circles Pick up your calculator for today’s notes

Radius Center Diameter Circumference d = 2r or r = d ÷ 2 The parts of a circle

Pi (  ) is an irrational number that is often approximated by the rational numbers 3.14 and The circumference of a circle is the distance around the circle. The area of a circle is the number of square units needed to cover the circle.

A. Circle with a radius of 4 m C = 2  r = 2  (4) = 8  m B. Circle with a diameter of 3.4 ft C =  d =  (3.4) = 3.4  ft Find the circumference of each circle, both in terms of  and to the nearest hundredth. Use 3.14 for . = m = 8 * 3.14 = ft = 3.4 * 3.14 = ft 4m 3.4 ft

A =  (4 2 ) = in 2 A. Circle with a radius of 4 in. Find the area of each circle, both in terms of  and to the nearest hundredth. Use 3.14 for . B. Circle with a diameter of 3.4 m  (1.7 2 ) = 2.89  m 2 d2d2 = 1.7 A =  r 2 = 16  in 2 = 16 * 3.14 A =  r 2 = 9.07 m 2 = m 2 = 2.89 * in 3.4 m

C =  d = 176 ft = (56) What is the circumference of a circle with a diameter of 56 feet? Use for  =  (56) = = 56 ft Remember, we are multiplying so we are allowed to cancel before getting our answer

d = or r = The parts of a circle

Pi (  ) is an number that is often approximated by the rational numbers and The circumference of a circle is The area of a circle is

A. Circle with a radius of m C = 2  r = = B. Circle with a diameter of ft C =  d = = Find the circumference of each circle, both in terms of  and to the nearest hundredth. Use 3.14 for . = = = = =

A = = A. Circle with a radius of in. Find the area of each circle, both in terms of  and to the nearest hundredth. Use 3.14 for . B. Circle with a diameter of m  = = A =  r 2 = = A =  r 2 = = =

C = = = ( ) 22 7 What is the circumference of a circle with a diameter of 56 feet? Use for . = = = ft