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McGraw Hill Glencoe Geometry, 2012

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McGraw Hill Glencoe Geometry, 2012 View details

2. Areas of Trapezoids, Rhombi, and Kites

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Exercise 53 Page 796

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

Circumference: 18.8in.
Area: 28.3in.^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 formula below. C=2π rFrom the figure, we know that the radius of the circle is 3 inches. By substituting 3 for r in the formula, we can calculate C.

C=2π r

r= 3

C=2π( 3)

Multiply

C=6π

Use a calculator

C=18.849555...

Round to 1 decimal place(s)

C ≈ 18.8

The circumference of the circle is approximately 18.8 inches.

Area

Similar to the perimeter, the area of a circle with radius r is calculated using the formula below. A=π r^2 From the figure, we know that the radius of the circle is 3 inches. By substituting 3 for r in the formula, we can calculate A.

A=π r^2

r= 3

A=π( 3)^2

Calculate power

A=π * 9

Use a calculator

A=28.274333...

Round to 1 decimal place(s)

A ≈ 28.3

The area of the circle is approximately 28.3 square inches.

Subchapter links

Check Your Understanding p.793

H.O.T. Problems p.795

Standardized Test Practice p.796

Spiral Review p.796

Skills Review p.796