Lesson 6-8 Pages 270-273

Geometry: Perimeter and

AreaLesson Check 6-7

What you will learn!

How to find the perimeters and areas of figures.

PerimeterPerimeterFormulaFormulaAreaArea

What you really need to know!

The distance around a geometric figure is called the perimeter. To find the perimeter of any geometric figure, add the measures of its sides.

9 units

5 units

9

5

Perimeter = 28 units

What you really need to know!

The perimeter of a rectangle is twice the length l plus twice the width w.

P = 2l + 2w

9 units

5 units

9

5

Perimeter = 28 units

P = 2l + 2wP = 2×9 + 2×5P = 18 + 10P = 28

What you really need to know!

The measure of the surface enclosed by a geometric figure is called the area.

9 units

5 units

Area = 45 units2

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18

19 20 21 22 23 24 25 26 27

28 29 30 31 32 33 34 35 36

37 38 39 40 41 42 43 44 45

What you really need to know!

The area of a rectangle is the product of the length l and width w.

A= L × W

Area = l × w

Length (9 units)

Width

(5 units)

Area = 9 × 5Area = 45 units2

Example 1:

Find the perimeter of the rectangle:

18 ft2

ft

P = 2l + 2wP = 2•18 + 2•2

40 ft

4

3

4

3

8

12

8

31

4

12

in4

17

Example 2: Find the perimeter:

Example: 3 Find the area of the surface of the reservoir shown below.

4 mi

5/8 mi

A = lw

2

2

12

8

54 mia

Page 272

Guided Practice

#’s 3-7

Pages 270-271 with someone at home and study

examples!

Read:

Homework: Page 272-273

#’s 8-28 even

#’s 30-43

Lesson Check 6-8

Page

579

Lesson 6-8

Lesson Check 6-8

Homework: Page 272-273

#’s 8-17, 23-27 all

#’s 30-43