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McGraw Hill Glencoe Geometry, 2012

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McGraw Hill Glencoe Geometry, 2012 View details

6. Two-Dimensional Figures

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Exercise 22 Page 62

Do you remember the formulas for finding the circumference and the area of a circle?

Circumference: 25.1cm
Area: 105.7cm^2

Practice makes perfect

Let's find the circumference and the area of the circle separately.

Circumference

The circumference C of a circle with radius r is calculated using the following formula. C=2π rFrom the figure, we know that the radius of the circle is 5.8cm. By substituting 5.8 for r in the formula, we can calculate C.

C=2π r

r= 5.8

C=2π( 5.8)

Multiply

C=11.6 π

Use a calculator

C=36.4424747 ...

Round to 1 decimal place(s)

C≈ 36.4

The circumference of the circle is approximately 36.4cm.

Area

Similar to the perimeter, the area of a circle with radius r is calculated using a well-known formula. A=π r^2 We know that the radius of the circle is 5.8cm. By substituting 5.8 for r in the formula, we can calculate A.

A=π r^2

r= 5.8

A=π( 5.8)^2

Calculate power

A=π (33.64)

Use a calculator

A=105.68317 ...

Round to 1 decimal place(s)

A≈ 105.7

The area of the circle is approximately 105.7cm^2.

Subchapter links

Check Your Understanding p.61

Practice and Problem Solving p.61-63

H.O.T. Problems p.63

Standardized Test Practice p.64

Spiral Review p.64

Skills Review p.64