Practice A Circles and Circumference Point G is the center of the circle. Use it to answer each question. 1. Name the circle. 2. Name the diameter. 3. Name three radii. Find each missing value to the nearest hundredth. Use 3.14 for π. 4. 5. C = 6. A builder is putting in a circular window. Find the circumference by rounding π to 3. What is the circumference if the diameter is 10 feet? C = 7. A builder is putting in a circular garden. Find the circumference by rounding π to 3. What is the circumference if the radius is 5 yards? 8. Students in England created the world s largest yo-yo. Its diameter is about 10 feet long! What is the circumference of the yo-yo? 9. The Mayall Telescope at Kitt Peak National Observatory in Arizona has a lens with a 2-meter radius. This glass lens is covered with a thin sheet of reflective aluminum. What is the circumference of the aluminum sheet?
Practice B Circles and Circumference Use the circle to answer each question. 1. Name the circle. 2. Name two diameters. 3. Name four radii. 4. Name three chords Find each missing value to the nearest hundredth. Use 3.14 for π. 5. 6. C = C = A gardener is putting in a circular garden. The inner circle is a vegetable garden, and the outer circle is a flower garden. Find the circumference by rounding π to 3. 7. If the diameter of the vegetable garden is 6 feet, what is its circumference? 8. If the radius of the entire garden is 8 feet, what is its circumference? 9. The first Ferris wheel was built in 1893 in Chicago. Its diameter was 250 feet. How many feet did the passengers rotate with each complete turn? Use 3.14 for π. 10. Stonehenge, a circle of large carved stones in England, was built more than 1,000 years ago. The circle of stones has a diameter of 108 feet. What is the circumference of Stonehenge?
Practice C Circles and Circumference Use the circle to answer each question. 1. Label the center of the circle P. 2. Draw and label its diameter RO. 3. Label point Q on the circle. Then name three radii. 4. Label points S and T on the circle. Then name two chords. Find each missing value to the nearest hundredth. Use 3.14 for π. 5. 6. d = r = A builder is putting in a circular window. The inner circle is clear glass, and the outer circle is stained glass. Find the circumference by rounding π to 3. 7. If the diameter of the clear glass is 4 feet, what is its circumference? 8. If the radius of the whole glass is 6 feet, what is its circumference? 9. The diameter of a sandwich cookie is 1.75 inches. To the nearest tenth, what is the combined area of the two wafer parts of the sandwich cookie? Use 3.14 for π.
Review for Mastery 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. A line segment with an endpoint at the center and an endpoint on the circle is called the radius r. A line segment with both endpoints on the circle is called a chord. A line segment with both endpoints on the circle, and which also passes through the center is called the diameter d. The length of the diameter is twice the radius. This is circle P. PQ and PR are radii. QR is a diameter. QR and ST are chords. Identify each part of the circle. 1. center 4. chord 2. diameter 3. two radii The distance around a circle is called the circumference. The ratio of the circumference of a circle to its diameter is always the same. This relationship is called pi and is represented by the Greek letter π. Pi is a decimal number that has no end and never repeats. 3.14, or 22 7, is used to estimate pi. To find the circumference C of a circle, use a formula. C = πd 3.14 6 18.84 The circumference is about 18.84 units. Find the circumference. Use 3.14 for π. 5. 6.
Challenge Cheesy Pies Have you ever seen strips of cheese placed around the edge of an apple pie? I am sure you will agree that cheesy pies sound very tasty indeed. Find the circumference of each pie. Use 3.14 for π. Then find the total length in inches of the cheese strips in each box. Imagine placing the strips around the circumference of the pies. Which box of cheese strips would be best to buy for each pie? Draw a line from the pie to the appropriate box of cheese strips. 1. A. 2. Circumference B. Length = 3. Circumference C. Length = Circumference 4. Length = D. Circumference
Problem Solving Circles and Circumference Use the table to answer each question. Use 3.14 for π. 1. Which coin has the smallest radius? How long is that coin s radius? 2. What is the circumference of a nickel? 3.What is the circumference of a quarter? 4. Which coin has a greater circumference, a dollar or half dollar? What is the difference in their circumferences? 5. If you rolled a dollar coin on its edge, how far would it go with each complete turn? Circle the letter of the correct answer. 7. A dime has 118 ridges evenly spaced along its circumference. About how wide is each ridge? A about 0.24 mm B about 0.48 mm C about 0.15 mm D about 0.08 mm 9. You have two coins with a total circumference of 116.18 mm. How much money do you have? A $0.02 C $0.11 B $0.06 D $0.35 Official U.S. Coin Size Diameter (rounded to Coin nearest mm) Penny 19 Nickel 21 Dime 18 Quarter 24 Half Dollar 31 Dollar 27 6. Which U.S. coins will fit in a vending machine coin slot that is 2 centimeters wide? 8. The engraved words United States of America run about one-half the circumference of all U.S. coins. On which coin will the words run about 38 mm? F penny G dime H quarter J half dollar 10. You have three coins with a total circumference of 216.66 mm. How much money do you have? F $0.15 H $0.30 G $0.25 J $0.55
Reading Strategies Focus on Vocabulary A circle is a closed curve with all points on the figure the same distance from a center point. The radius of a circle is a line segment connecting the center of the circle to a point on the circle. A chord of a circle is a line segment with both endpoints on the circle. The diameter of a circle is a line segment that passes through the center of the circle and connects two points on the circle. The diameter is twice the length of a radius. The circumference is the distance around a circle. Use the pictures and definitions to name the figure described in each exercise. Write circle, center, radius, chord, diameter or circumference. 1. All the points on a circle are equidistant from this point. 2. a line segment with one endpoint at the center of the circle and the other endpoint on the circle 3. a line segment that has both endpoints on the circle 4. the distance around a circle 5. a closed figure with all points the same distance from a center 6. a segment that is twice the length of a radius
Puzzles, Twisters & Teasers Circular Reasoning Find the circumference of the circles by using 3.14 for π. Each answer is on the large circle at the bottom of the page. Near each answer on the large circle, write the letter that corresponds to it. 1. C 2. E 3. R 4. L 5. I 6. E 7. S 8. C 9. I 10. M What kind of circle do truck drivers like? A
Answers LESSON CODE 60908 1. A 2. BC Practice A 1. circle G 2. HJ 3. GH, GK, GJ 4. 3.14 in. 5. 18.84 m 6. 30 feet 7. 30 yards 8. about 31.4 feet 9. 12.56 meters Practice B 1. circle X 3. AB and AC 4. BC 5. C 25.12 units 6. C 12.56 units Challenge 1. A. 2. B. 2. YW and VZ 3. XV, XW, XZ, and XY 4. WY, VZ, and UT 5. 15.7 in. 6. 75.36 m 7. 18 feet 8. 48 feet 9. 785 feet 10. 339.12 feet 3. C. 4. D. Practice C 1 3. 3. PQ, PR, and PO 4. RO and ST 5. 28 in. 6. 2.5 m 7. 12 feet 8. 36 feet 9. 4.8 in 2 Review for Mastery Problem Solving 1. dime; 9 mm 2. 65.94 mm 3. 75.36 mm 4. half dollar; 12.56 mm 5. 84.78 mm 6. penny and dime 7. B 8. H 9. C 10. J Reading Strategies 1. center 2. radius
3. chord 4. circumference 5. circle 6. diameter Puzzles, Twisters & Teasers 1. 197.82 m 2. 43.96 m 3. 175.84 m 4. 10.99 m 5. 131.88 m 6. 56.52 m 7. 15.7 m 8. 75.36 m 9. 69.08 m 10. 50.24 m A S E M I C I R C L E