1.7 Perimeter,

Circumference, & Area

1.7 Perimeter,

Circumference, & Area

WHAT’S IMPORTANT:--Be able to find the perimeter & area of

common plane figures.--Be able to use a problem solving plan.

WHAT’S IMPORTANT:--Be able to find the perimeter & area of

common plane figures.--Be able to use a problem solving plan.

• On the following slides, you will see the perimeter, circumference, and area formulas for some basic geometric shapes. We will use these formulas throughout the lesson.

• Perimeter & circumference use units such as centimeters (cm), meters (m), inches (in), feet (ft), yards (yd), & miles (mi).

• The measurements of area use units such as square centimeters (cm2), square inches (in2), & so on.

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38 in.

200 mm

50.24 sq. cm.

25.12 cm.

84 sq. in.

119 sq ft.

9.7 in

15.7 cm

19.63 sq. cm.

547.2 mm

308.94 sq. ft.

5.2 sq. in.

Example Find the perimeter & area of the

rectangle shown

• P = 2x + 2y

• P = 2(13) + 2(4)

• P = 26 + 8

• P = 34 in.

• A = xy

• A = 13(4)

• A = 52 in2

13 in.

4 in.

Example: The diameter of a circle is shown. find the radius. then use that to find the circumference and area.

• r = (1/2)d

• r = (1/2)(14)

• r = 7in.

• C = 2∏r

• C = 2∏(7)

• C = 2(3.14)(7)

• C = 43.96 in.

• A = ∏r2

• A = (3.14)(72)

• A = (3.14)(49) = 153.86 in2

14 in.

F

ExamplePlot the Points & Find the area & perimeter of the triangle defined

by D(1,2), E(6,2), & F(3,5)

ExamplePlot the Points & Find the area & perimeter of the triangle defined

by D(1,2), E(6,2), & F(3,5)

Plot the points.Draw the height from point F to the base DE. Label the point GPoint G has the coordinates (3,2)

Plot the points.Draw the height from point F to the base DE. Label the point GPoint G has the coordinates (3,2)

Cont. Example...• To find the area, we need to find the lengths of the

base (DE) & the height (FG)

• DE = 6 - 1 = 5

• FG = 5 - 2 = 3

• A = (1/2)

• A = (1/2)(5)(3)

• A = (1/2)(15)

• A = 7.5 sq. units

Plot the Points & Find the area & perimeter of the triangle defined

by D(1,2), E(6,2), & F(3,5)• We need to find the lengths of all sides.

• We know the base is 5 units

• Now we must find the lengths of EF & DF.

Plot the Points & Find the area & perimeter of the triangle defined

by D(1,2), E(6,2), & F(3,5)

•Add to find the perimeter

•5 + 4.24 + 3.61

•Perimeter = 12.85 units

find the area of the figure below

find the area of the figure below

Draw a horizontal line to separate the figure into 3 non-overlapping figures: a rectangle & 2 squares.

Draw a horizontal line to separate the figure into 3 non-overlapping figures: a rectangle & 2 squares.

Find each area by adding• Area of the Rectangle

• A = bh

• A = (15)(5)

• A = 75

• Area of the Square

• A = s 2

• A = (5)2

• A = 25

• Add the areas

• A = 75 + 25 + 25

• A = 125 ft 2

• Therefore the area of the figure is 125 ft 2.