Finding Area and Circumference of a Circle Finding

Finding Area and Circumference of a Circle

Finding Area and Circumference of a Circle Patricia buys a round dinner table. The radius of dinner table is 6 meters. What is the area of table? Draw a picture: Choose formula: Substitute and solve: 6 m A = πr 2 A = 3. 14(6)2 A = 113 m 2

Finding Area and Circumference of a Circle Steven purchases a bowl. The diameter of the bowl is 14 cm. What is the circumference of the bowl? Draw a picture: Choose formula: Substitute and solve: 14 cm C = πd C = 3. 14(14) C = 44 cm

Finding Area and Circumference of a Circle Daniel wants to buy cookies for his friend. The radius of a cookie is 5 inches. What is the cookie’s circumference? Draw a picture: Choose formula: Substitute and solve: 5 in C = 2πr C = 2(3. 14)(5) C = 31. 4 in

Finding Area and Circumference of a Circle Donna makes a round pizza. She wants to put a cheese layer on the pizza. If the cake is 8 cm in diameter, how many square cm of cheese layer does she need to put on the pizza? Draw a picture: Choose formula: Substitute and solve: 8 cm We know diameter, but need radius A = πr 2 Radius is one half the diameter, so r = 4 cm A = (3. 14)(4)2 A = 50. 24 cm 2

Finding Area and Circumference of a Circle Charles has a circular carpet in his drawing room. He wants to put a circular table in middle of the carpet. The diameter of the carpet is 12 meters and the diameter of the table is 4 meters. Calculate how much area of carpet is left after putting the table in place? What are we looking for? Draw a picture: 12 m 4 m Choose formula: A = πr 2 Substitute and solve: Area of the carpet remaining (blue) Subtract the small circle from the big circle We know d but we need r A(carpet) – A(table) A =(3. 14)(6)2 – (3. 14)(2)2 A = 113 – 13 = 100 m 2

Finding Area and Circumference of a Circle A circular fountain has a diameter of 10 meters. The statue in the middle has a diameter of 1 meter. What is the area of the bottom of the fountain? What are we looking for? Draw a picture: 10 m 1 m Area of the bottom of fountain (blue) Subtract the small circle from the big circle We know d but we need r Choose formula: A = πr 2 Substitute and solve: A(fountain) – A(statue) A =(3. 14)(5)2 – (3. 14)(0. 5)2 A =78. 5 – 0. 79 = 77. 71 m 2