EXAMPLE 1
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EXAMPLE 1 Using Radius to Find Circumference Find the circumference of a circle with a radius of 11 meters. SOLUTION C = 2πr Circumference formula 2(3.14)(11) Substitute 3.14 for π and 11 for r. = 69.08 Multiply. ANSWER The circumference is about 69.08 meters.
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2(3.14)( 11 ). ANSWER. The circumference is about 69.08 meters. EXAMPLE 1. Using Radius to Find Circumference. Find the circumference of a circle with a radius of 11 meters. SOLUTION. C = 2π r. Circumference formula. Substitute 3.14 for π and 11 for r. = 69.08. Multiply. - PowerPoint PPT Presentation
Transcript of EXAMPLE 1
EXAMPLE 1 Using Radius to Find Circumference
Find the circumference of a circle with a radius of 11 meters.
SOLUTION
C = 2πr Circumference formula
2(3.14)(11) Substitute 3.14 for π and 11 for r.
= 69.08 Multiply.
ANSWER
The circumference is about 69.08 meters.
EXAMPLE 2 Using Diameter to Find Circumference
SOLUTION
The measure shown is a diameter, so use the circumference formula that involves the diameter.
C = πd Circumference formula
Substitute. Use for π because 21 is divisible by 7.
22 7
22
71
. 213
Multiply= 66
Find the circumference of the circle.
ANSWER The circumference is about 66 feet.
EXAMPLE 3 Standardized Test Practice
SOLUTION
You are asked to find the diameter, so use the circumference formula that involves diameter.
C = πd Circumference formula
423.9 3.14d Substitute 423.9 for C and 3.14 for π.
423.9 3.14
=3.14d 3.14
Divide each side by 3.14.
135 = d Simplify.
ANSWERThe diameter is about 135 feet. The correct answer is C.
GUIDED PRACTICE for Examples 1, 2, and 3
Find the circumference of the circle. Use 3.14 or for π . Explain your choice of π .
22 7
1.
Use for π because 28 is divisible by 7.
22 7
ANSWER The circumference is about 176 mi.
GUIDED PRACTICE for Examples 1, 2, and 3
2.
Use 3.14 for π because 9.5 is not divisible by 7.
ANSWER The circumference is about 59.66 m.
Find the circumference of the circle. Use 3.14 or for π . Explain your choice of π .
22 7
GUIDED PRACTICE for Examples 1, 2, and 3
3.
Use 3.14 for π because 16 is not divisible by 7.
ANSWER The circumference is about 50.24 cm.
Find the circumference of the circle. Use 3.14 or for π . Explain your choice of π .
22 7
GUIDED PRACTICE for Examples 1, 2, and 3
4. diameter = 32 in.
Use 3.14 for π because 32 is not divisible by 7.
ANSWER The circumference is about 100.48 cm.
GUIDED PRACTICE for Examples 1, 2, and 3
5. diameter = 140 ft.
ANSWER The circumference is about 440 ft.
Use for π because 140 is divisible by 7.
227
GUIDED PRACTICE for Examples 1, 2, and 3
Use 3.14 for π because 1.5 is not divisible by 7.
ANSWER The circumference is about 9.42 cm.
6. radius = 1.5 km
GUIDED PRACTICE for Examples 1, 2, and 3
7. What If? In Example 3, suppose the circumference of the Ferris wheel is 462 feet. What is the diameter of the Ferris wheel?
ANSWER The diameter is about 147 feet.
