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McGraw Hill Integrated II, 2012

MH

McGraw Hill Integrated II, 2012 View details

Study Guide and Review

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Exercise 15 Page 792

Use the formula for the circumference of a circle to find the diameter and radius.

Diameter: 34.54ft
Radius: 17.27ft

Practice makes perfect

Let's find the diameter and radius of the circle. The circumference C of a circle with radius r is calculated using the formula below. C=2π rFrom the exercise, we know that the circumference of the circle is 108.5ft. Let's substitute it for C into the formula, to calculate r.

C=2π r

C= 108.5

108.5=2π r

▼

Solve for r

.LHS /2π.=.RHS /2π.

108.5/2π=r

Rearrange equation

r=108.5/2π

Use a calculator

r=17.268...

Round to 2 decimal place(s)

r≈ 17.27

The radius of the circle is approximately 17.27ft. Now, to find the diameter, we can multiply the radius by 2. Let's use the exact value of the radius.

d=2r

r= 108.5/2π

d=2( 108.5/2π)

▼

Simplify right-hand side

MoveLeftFacToNum

a*b/c= a* b/c

d=217/2π

a/b=.a /2./.b /2.

d=108.5/π

Use a calculator

d=34.536...

Round to 2 decimal place(s)

d≈ 34.54

The diameter of the circle is approximately 34.54ft.

Subchapter links

1 Circles and Circumference p.792

2 Measuring Angles and Arcs p.792

3 Arcs and Chords p.793

4 Inscribed Angles p.793

5 Tangents p.794

6 Secants, Tangents, and Angle Measures p.794

7 Special Segments in a Circle p.795

8 Equations of Circles p.795

9 Areas of Circles and Sectors p.796