Lesson 12.1 Skills Practice Introduction to ircles ircle, Radius, and iameter Vocabulary efine each term in your own words. 1. circle circle is a collection of points on the same plane equidistant from the same point. 2. center of a circle The center of a circle is the point from which all points on the circle are equidistant. 3. radius of a circle The radius of a circle is a line segment formed by connecting a point on the circle and the center of the circle. 4. diameter of a circle The diameter of a circle is a line segment formed by connecting two points on the circle such that the line segment passes through the center point. Problem Set Use the circle shown to answer each question. 1. Name the circle. The circle shown is ircle. 2. Identify a radius of the circle. E Line segment is a radius of the circle. F 3. Identify a diameter of the circle. Line segment EF is a diameter of the circle. hapter 12 Skills Practice 789
Lesson 12.1 Skills Practice page 2 4. Name the circle. The circle shown is ircle. F 5. Identify a radius of the circle. E Line segment is a radius of the circle. G 6. Identify a diameter of the circle. Line segment E is a diameter of the circle. 7. Identify a different diameter of the circle. Line segment FG is a diameter of the circle. 8. Name the circle. The circle shown is ircle. 9. Identify a radius of the circle. Line segment is a radius of the circle. E 10. Identify a diameter of the circle. Line segment is a diameter of the circle. F 790 hapter 12 Skills Practice
Lesson 12.1 Skills Practice page 3 etermine if the circles are congruent. 11. E Line segment is a radius of ircle and is 2 centimeters. Line segment E is a diameter of ircle and is 4 centimeters. The diameter of ircle equals 4 centimeters. The diameter of ircle equals the diameter of ircle. ircle and ircle are congruent. 12. Line segment is a radius of ircle and is 7 inches. Line segment is a radius of ircle and is 12 inches. The radius of ircle does not equal the radius of ircle. ircle and ircle are not congruent. hapter 12 Skills Practice 791
Lesson 12.1 Skills Practice page 4 13. The radius of ircle is 5 centimeters. The radius of ircle is 5 centimeters. The radius of ircle equals the radius of ircle. ircle and ircle are congruent. 14. The diameter of ircle is 7 millimeters. The radius of ircle is 7 millimeters. The diameter of ircle equals 14 millimeters. The diameter of ircle does not equal the diameter of ircle. ircle and ircle are not congruent. 15. The radius of ircle is 3 inches. The diameter of ircle is 6 inches. The diameter of ircle equals 6 inches. The diameter of ircle equals the diameter of ircle. ircle and ircle are congruent. 16. The radius of ircle is 5 centimeters. The radius of ircle is 8 centimeters. The radius of ircle does not equal the radius of ircle. ircle and ircle are not congruent. 17. The radius of ircle is 4 inches. The diameter of ircle is 7 inches. The diameter of ircle equals 8 inches. The diameter of ircle does not equal the diameter of ircle. ircle and ircle are not congruent. 18. The diameter of ircle is 12 centimeters. The radius of ircle is 6 centimeters. The diameter of ircle equals 12 centimeters. The diameter of ircle equals the diameter of ircle. ircle and ircle are congruent. 792 hapter 12 Skills Practice
Lesson 12.1 Skills Practice page 5 onstruct each figure using congruent circles. 19. onstruct an equilateral triangle using congruent circles. 20. onstruct an equilateral quadrilateral using congruent circles. 21. onstruct an equilateral hexagon using congruent circles. F E hapter 12 Skills Practice 793
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Lesson 12.2 Skills Practice ut Most of ll, I Like Pi! ircumference of a ircle Vocabulary efine the term in your own words. 1. pi The number pi (p) is the ratio of the circumference of a circle to its diameter. Problem Set Use a string and a centimeter ruler to measure the radius and circumference of each circle. alculate the ratio of the circumference of the circle to its diameter. 1. nswers will vary. The ratio should be 3.14. 2. 3. nswers will vary. The ratio should be 3.14. nswers will vary. The ratio should be 3.14. hapter 12 Skills Practice 795
Lesson 12.2 Skills Practice page 2 4. nswers will vary. The ratio should be 3.14. 5. E nswers will vary. The ratio should be 3.14. 6. F nswers will vary. The ratio should be 3.14. 796 hapter 12 Skills Practice
Lesson 12.2 Skills Practice page 3 alculate each value using the formula for the circumference of a circle. Round your answer to the nearest hundredth, if necessary. 7. The diameter of a circle is 6 centimeters. alculate the circumference of the circle using the 5 pd 5 (3.14)(6) 5 18.84 The circumference of the circle is 18.84 centimeters. 8. The radius of a circle is 8.2 centimeters. alculate the circumference of the circle using the 5 2pr 5 2(3.14)(8.2) 51.50 The circumference of the circle is approximately 51.50 centimeters. 9. The diameter of a circle is 7.5 inches. alculate the circumference of the circle using the 5 pd 5 (3.14)(7.5) 5 23.55 The circumference of the circle is 23.55 inches. hapter 12 Skills Practice 797
Lesson 12.2 Skills Practice page 4 10. The radius of a circle is 16.3 millimeters. alculate the circumference of the circle using the 5 2pr 5 2(3.14)(16.3) 102.36 The circumference of the circle is approximately 102.36 millimeters. 11. The diameter of a circle is 14 centimeters. alculate the circumference of the circle using the 5 pd 5 (3.14)(14) 5 43.96 The circumference of the circle is 43.96 centimeters. 12. The radius of a circle is 2.1 inches. alculate the circumference of the circle using the 5 2pr 5 2(3.14)(2.1) 13.19 The circumference of the circle is approximately 13.19 inches. 798 hapter 12 Skills Practice
Lesson 12.2 Skills Practice page 5 alculate each value using the formula for the circumference of a circle. Round your answer to the nearest hundredth, if necessary. 13. The circumference of a circle is 56 centimeters. alculate the diameter of the circle using the 5 pd 56 5 (3.14)d 56 3.14 5 3.14d 3.14 17.83 d The diameter of the circle is approximately 17.83 centimeters. 14. The circumference of a circle is 25.12 centimeters. alculate the radius of the circle using the 5 2pr 25.12 5 2(3.14)r 25.12 5 6.28r 4 5 r The radius of the circle is 4 centimeters. hapter 12 Skills Practice 799
Lesson 12.2 Skills Practice page 6 15. The circumference of a circle is 112.8 millimeters. alculate the diameter of the circle using the 5 pd 112.8 5 (3.14)d 35.92 d The diameter of the circle is approximately 35.92 millimeters. 16. The circumference of a circle is 49.6 inches. alculate the radius of the circle using the 5 2pr 49.6 5 2(3.14)r 49.6 5 6.28r 7.90 r The radius of the circle is approximately 7.90 inches. 800 hapter 12 Skills Practice
Lesson 12.2 Skills Practice page 7 17. The circumference of a circle is 47.73 millimeters. alculate the diameter of the circle using the 5 pd 47.73 5 (3.14)d 15.20 d The diameter of the circle is approximately 15.20 millimeters. 18. The circumference of a circle is 56.52 centimeters. alculate the radius of the circle using the 5 2pr 56.52 5 2(3.14)r 56.52 5 6.28r 9 5 r The radius of the circle is 9 centimeters. hapter 12 Skills Practice 801