Study Guide and Intervention Geometry: Circles and Circumference A circle is the set of all points in a plane that are the same distance from a given point, called the center. The diameter d is the distance across the circle through its center. The radius r is the distance from the center to any point on the circle. The circumference C is the distance around the circle. The circumference C of a circle is equal to its diameter d times, or times its radius r times. radius center circumference diameter Find the circumference of a circle with a diameter of 7.5 centimeters. C d C 3.14 7.5 C 3.55 Use 3.14 for. The circumference of the circle is about 3.55 centimeters. If the radius of a circle is 14 inches, what is its circumference? C r C 14 Use for. 7 7 C 88 The circumference of the circle is about 88 inches. Find the circumference of each circle. Use 3.14 or for. Round to 7 the nearest tenth if necessary. 1.. 3. 4. 6 ft 0 cm 5. diameter 15 km 6. radius 1 mi 7. radius 50 m 5 m 7.5 in. Lesson 6 9 8. diameter 600 ft 9. radius 6 mm 10. diameter 7 km 11. radius 95 in. 1. diameter 6.3 m 13. diameter 5 1 cm 4 Glencoe/McGraw-Hill 343 Mathematics: Applications and Concepts, Course
NAME DATE PERIOD Practice: Skills Geometry: Circles and Circumference Find the circumference of each circle. Use 3.14 or the nearest tenth if necessary. 1.. 7 for. Round to 4 in. 15 cm 3. 4. 8 ft 1 m 5. 6. 16 km 37 mm 7. radius 3 km 8. radius 46 cm 9. diameter 30 in. 10. diameter 5 m 11. radius 5 ft 1. diameter 9 1 in. 13. radius 3 1 ft 14. diameter 9.7 mm 15. radius 5. km 16. diameter 5 m 17. radius ft 18. diameter 9.4 in. 19. radius 100 m 0. radius 65 mi 1. diameter 10 1 in.. diameter 8.5 cm Glencoe/McGraw-Hill 344 Mathematics: Applications and Concepts, Course
Practice: Word Problems Geometry: Circles and Circumference 1. PLATES A manufacturing company is producing dinner plates with a diameter of 1 inches. They plan to put a gold edge on each plate. Determine how much gold edging they need for each plate by finding the circumference of each plate. Round to the nearest tenth.. MONEY A dime has a radius of 8 1 millimeters. Find the circumference of a dime to the nearest tenth. 3. MERRY-GO-ROUND Mr. Osterhout is putting trim around the edge of a circular merry-go-round that has a diameter of 15 feet. How much trim does he need to buy to the nearest tenth? 4. PIZZA Find the circumference of a pizza with a diameter of 10 inches. Round to the nearest tenth. 5. RACING A circular racetrack has a diameter of 1 mile. How far does a car travel in one lap around the track? Round to the nearest tenth. 6. TIRE A bicycle tire has a radius of 15 inches. What is the circumference of the tire? Round to the nearest tenth. 7. EQUATOR Earth s diameter at the equator is 7,96 miles. Find the distance around Earth at its equator to the nearest tenth. 8. SATURN The ring system around Saturn has a diameter of 170,000 miles. Find the circumference of the ring system. Lesson 6 9 Glencoe/McGraw-Hill 345 Mathematics: Applications and Concepts, Course
Study Guide and Intervention Area of Circles The area A of a circle equals the product of pi ( ) and the square of its radius r. A r Find the area of the circle. A r Area of circle 5 cm A 5 Replace r with 5. ENTER 5 78.53981634 The area of the circle is approximately 78.5 square centimeters. Find the area of a circle that has a diameter of 9.4 millimeters. A r Area of a circle A 4.7 Replace r with 9.4 or 4.7. A 69.4 Use a calculator. The area of the circle is approximately 69.4 square millimeters. Find the area of each circle. Round to the nearest tenth. 1.. 3. 7 in. 5 mm 1 ft 4. radius.6 cm 5. radius 14.3 in. 6. diameter 5 1 yd 7. diameter 4 3 4 mi 8. diameter 7.9 mm 9. radius 1 ft 5 Glencoe/McGraw-Hill 634 Mathematics: Applications and Concepts, Course
Practice: Skills Area of Circles Find the area of each circle. Round to the nearest tenth. 1.. 4 yd 1 cm 3. 4. 35 mm 14 in. Lesson 11 6 5. 6. 4.3 ft 8 cm 7. 8. 4.7 yd.5 in. 9. 10..1 mm 11.9 ft 11. radius 5.7 mm 1. radius 8. ft 13. diameter 3 1 in. 14. diameter 15.6 cm 4 15. radius 1.1 in. 16. diameter 1 3 yd 4 Glencoe/McGraw-Hill 635 Mathematics: Applications and Concepts, Course
Practice: Word Problems Area of Circles 1. POOLS Susan designed a circular pool with a diameter of 5 meters. What is the area of the bottom of the pool? Round to the nearest tenth.. MONEY Find the area of the coin to the nearest tenth. 19 mm 3. DRUMS What is the area of the drumhead on the drum shown below? Round to the nearest tenth. 4. PIZZA Estimate the area of the top of a round pizza that has a diameter of 16 inches. Round to the nearest tenth. 14 in. 5. GARDENING Jane needs to buy mulch for the garden with the dimensions shown in the figure. For how much area does Jane need to buy mulch? Round to the nearest tenth. 6. UTILITIES What is the area of the top surface of a circular manhole cover that has a radius of 30 centimeters? Round to the nearest tenth. 5.5 yd Glencoe/McGraw-Hill 636 Mathematics: Applications and Concepts, Course