EXAMPLE 1 Use the formula for circumference Find

EXAMPLE 2 Use circumference to find distance traveled Tire Revolutions The dimensions of a

EXAMPLE 2 Use circumference to find distance traveled STEP 3 Find the distance the

EXAMPLE 2 Use circumference to find distance traveled STEP 4 Use unit analysis. Change

GUIDED PRACTICE 1. for Examples 1 and 2 Find the circumference of a circle

GUIDED PRACTICE for Examples 1 and 2 circumference = 17 feet C = d

GUIDED PRACTICE 2. for Examples 1 and 2 A car tire has a diameter

for Examples 1 and 2 GUIDED PRACTICE STEP 3 Find the number of revolutions

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EXAMPLE 1 Use the formula for circumference Find the indicated measures. a. Circumference of a circle with radius 9 centimeters SOLUTION a. C = 2 πr =2 π 9 = 18 56. 55 Write circumference formula. Substitute 9 for r. Simplify. Use a calculator. ANSWER The circumference is about 56. 55 centimeters.

EXAMPLE 1 Use the formula for circumference Find the indicated measures. b. Radius of a circle with circumference 26 meters C = 2 πr 26 = r 2π 4. 14 r Write circumference formula. Substitute 26 for c. Divide each side by 2π. Use a calculator. ANSWER The radius is about 4. 14 meters.

EXAMPLE 2 Use circumference to find distance traveled Tire Revolutions The dimensions of a car tire are shown at the right. To the nearest foot, how far does the tire travel when it makes 15 revolutions? SOLUTION STEP 1 Find the diameter of the tire d = 15 + 2 (5. 5) = 26 in. STEP 2 Find the circumference of the tire C = πd = π(26) ≈ 81. 68 in.

EXAMPLE 2 Use circumference to find distance traveled STEP 3 Find the distance the tire travels in 15 revolutions. In one revolution, the tire travels a distance equal to its circumference. In 15 revolutions, the tire travels a distance equal to 15 times its circumference. 15 81. 68 in = 1225. 2 in

EXAMPLE 2 Use circumference to find distance traveled STEP 4 Use unit analysis. Change 1225. 2 inches to feet. 1225. 2 in. 1 ft = 102. 1 ft 12 in. ANSWER The tire travels approximately 102 feet.

GUIDED PRACTICE 1. for Examples 1 and 2 Find the circumference of a circle with diameter 5 inches. Find the diameter of a circle with circumference 17 feet. SOLUTION C= d =5 15. 71 Write circumference formula. Substitute 5 for d. Use a calculator. The circumference is about 15. 71 in.

GUIDED PRACTICE for Examples 1 and 2 circumference = 17 feet C = d Write circumference formula. d 17 = d Substitute 17 for c. 5. 41 Use a calculator. r Divide each side by π. The Diameter is about 5. 41 feet.

GUIDED PRACTICE 2. for Examples 1 and 2 A car tire has a diameter of 28 inches. How many revolutions does the tire make while traveling 500 feet? SOLUTION STEP 1 Find the circumference of the tire C = πd = π(28) ≈ 87. 92 in. STEP 2 Use unit analysis. Change 500 feet to inches. 500 ft. 12 in. = 6000 in. 1 ft

for Examples 1 and 2 GUIDED PRACTICE STEP 3 Find the number of revolutions 6000 N N = 68. 24 87. 92 ANSWER The tire makes 68. 2 revolutions.