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McGraw Hill Glencoe Geometry, 2012

MH

McGraw Hill Glencoe Geometry, 2012 View details

1. Circles and Circumference

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Exercise 25 Page 702

What is the formula for finding the circumference of a circle?

Radius: $19.74 ft$
Diameter: $39.47 ft$

Practice makes perfect

Let's find the radius and the diameter of the circle separately. The circumference

C

of a circle with radius

r

is calculated using the formula below.

C = 2 π r

From the exercise, we know that the circumference of the circle is

124 ft .

By substituting

124

for

C

in the formula, we can solve for

r .

C = 2 π r

$C = 124$

124 = 2 π r

$LHS / 2 = RHS / 2$

62 = π r

$LHS / π = RHS / π$

\frac{6 2}{π} = r

Rearrange equation

r = \frac{6 2}{π}

Use a calculator

r = 19.735212 \dots

Round to $2$ decimal place(s)

r \approx 19.74

The radius of the circle is approximately

19.74 ft .

Now, to find the diameter, we can multiply the radius by

2 .

2 \times \frac{6 2}{π} \approx 39.47 ft

Subchapter links

Check Your Understanding p.701

Practice and Problem Solving p.701-704

H.O.T. Problems p.704

Standardized Test Practice p.705

Spiral Review p.705

Skills Review p.705