169_186_CC_A_RSPC1_C12_662330.indd



Practice 7.9(B)SCORE __________Determine the circumference and area of circles.Multi-Step ExampleMary has a charm bracelet that creates a circle with an area of 3.8 square inches. If each charm on the bracelet is 0.25 inch wide, approximately how many charms can Mary put on the bracelet?A = πr2Area of a circle3.8 ≈ 3.14r2Substitute 3.8 for A and 3.14 for π.3.83.14 ≈ r2Divide both sides by 3.14.1.1 ≈ rTake the square root of both sides.Round to the nearest tenth.The radius is 1.1 inches, so the diameter is 2 ? 1.1 or 2.2 inches.Next, find the circumference.C = πdCircumference of a circleC ≈ 3.14 ? 2.2Substitute 3.14 for π and 2.2 for d.C ≈ 6.908Multiply.Finally, divide the circumference by the width of each charm: 6.9080.25 = 27.632.So, Mary can put 27 charms on the bracelet.1 Joe’s Coffee is having a stained glass window installed on their front door. Approximately how much glass will be needed to create the stained glass window? Use 3.14 for π.A 2.4 ft2B 9.6 ft2C 11 ft2D 38.5 ft22 The street signs in a subdivision are in the shape of circles. Each street sign has an area of 452.16 square inches. What is the approximate circumference of each sign? Use 3.14 for π.F 38G 72H 75J 1443 Elaina’s old bicycle had tires with a 12-inch diameter. Her new bicycle has tires with a 16-inch diameter. What is the difference in the circumference of the tires? Use 3.14 for πA 12.56 in. 29.14 in.C 37.68 in.D 50.24 in.Practice 7.9(B) (continued)SCORE __________4 Kim has two circular push pins on her bulletin board. The table shows the diameter length of each pin. What is the difference in area between the two push pins? Use 3.14 for π.Size of PinDiameter (in.)Large1.2Small0.44F 0.15 in2G 0.98 in2H 1.13in2J 1.28 in25 Sarah wants to cover the rim of her circular pool with a foam covering. The foam covering is sold in boxes that will cover 40 feet. How many boxes of foam will Sarah need to cover the rim of the pool? Use 3.14 for π.A 2 boxesB 3 boxesC 5 boxesD 7 boxes6 A construction crew is building a circular playground. The playground is surrounded by a fence that is 47.1 feet long. About how much area will the playground cover? Use 3.14 for π. Round to the nearest tenth.Record your answer and fill in the bubbles on your answer document. Be sure to use the correct place value.7 Thomas is training for a 3.1-mile race by running on a circular path. He knows that it is 0.75 mile from the tree in the center of the circular path to the path. How long is the path? Use 3.14 for π.F 1.8 mi 4.7 mi 6.7 miJ 7.1 mi8 Bessie is making an apple pie. The top of the pie pan is shown below. Approximately how much pie crust will Bessie need to cover the top of the pie? Use 3.14 for π.A 25 in2B 30 in2C 50 in2D 71 in29 Several students form a circle by standing next to each other. Samantha and Aaron are directly across from each other and are approximately 30 feet apart. If each student takes up about 4 feet of the circle, how many students are in the circle? Use 3.14 for π.Record your answer and fill in the bubbles on your answer document. Be sure to use the correct place value.Practice 7.9(B)SCORE __________Student Recording SheetFill in the correct answer. For gridded-response questions, write your answers in the boxes on the answer grid and fill in the bubbles to match your answers.123456789 ................
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