GEOMETRYHELP

Margaret’s garden is a square 12 ft on each side.

Margaret wants a path 1 ft wide around the entire garden.

What will the outside perimeter of the path be?

The perimeter is 56 ft.

P = 4s Formula for perimeter of a square

P = 4(14) = 56 Substitute 14 for s.

Because the path is 1 ft wide, increase each side of the garden by 1 ft. s = 1 + 12 + 1 = 14

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Perimeter, Circumference, and AreaLESSON 1-9

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GEOMETRYHELP

C = 2 (6.5) Substitute 6.5 for r.

The circumference of G is 13 , or about 40.8 cm..

C = 13 Exact answer

C = 2 r Formula for circumference of a circle

G has a radius of 6.5 cm. Find the circumference of G in

terms of . Then find the circumference to the nearest tenth.

. .

Perimeter, Circumference, and AreaLESSON 1-9

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C = 13 Use a calculator.

GEOMETRYHELP

Quadrilateral ABCD has vertices

A(0, 0), B(9, 12), C(11, 12), and D(2, 0).

Find the perimeter.

Draw and label ABCD on a coordinate plane.

BC = |11 – 9| = |2| = 2 Ruler Postulate

DA = |2 – 0| = |2| = 2 Ruler Postulate

Find the length of each side. Add the lengths to find the perimeter.

AB = (9 – 0)2 + (12 – 0)2 = 92 + 122 Use the Distance Formula.

= 81 + 144 = 255 = 15

CD = (2 – 11)2 + (0 – 12)2 = (–9)2 + (–12)2 Use the Distance Formula.

= 81 + 144 = 255 = 15

Perimeter, Circumference, and AreaLESSON 1-9

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GEOMETRYHELP

(continued)

Perimeter = AB + BC + CD + DA

= 15 + 2 + 15 + 2

= 34

The perimeter of quadrilateral ABCD is 34 units.

Perimeter, Circumference, and AreaLESSON 1-9

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GEOMETRYHELP

Write both dimensions using the same unit of measurement. Find the area of the rectangle using the formula A = bh.

36 in. = 3 ft Change inches to feet using 12 in. = 1 ft.

A = bh Formula for area of a rectangle.

A = (4)(3) Substitute 4 for b and 3 for h.

A = 12

You need 12 ft2 of fabric.

To make a project, you need a rectangular piece of fabric 36 in. wide and 4 ft long. How many square feet of fabric do you need?

Perimeter, Circumference, and AreaLESSON 1-9

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GEOMETRYHELP

A = r2 Formula for area of a circle.

A = (1.5)2 Substitute 1.5 for r.

A = 2.25

In B, r = 1.5 yd..

The area of B is 2.25 yd2..

Find the area of B in terms of . .

Perimeter, Circumference, and AreaLESSON 1-9

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GEOMETRYHELP

Find the area of the figure below.

Draw a horizontal line to separate the figure into three nonoverlapping figures: a rectangle and two squares.

Perimeter, Circumference, and AreaLESSON 1-9

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GEOMETRYHELP

AR = bh Formula for area of a rectangleAR = (15)(5) Substitute 15 for b and 5 for h.AR = 75

AS = s2 Formula for area of a squareAS = (5)2 Substitute 5 for s.AS = 25

A = 75 + 25 + 25 Add the areas. A = 125

The area of the figure is 125 ft2.

Find each area. Then add the areas.

(continued)

Perimeter, Circumference, and AreaLESSON 1-9

Additional Examples

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