Lesson 3-7 Pages 131-136

Using Formulas

What you will learn!1. How to solve problems by using formulas.

2. How to solve problems involving the perimeters and areas of rectangles.

FormulaFormulaPerimeterPerimeterAreaArea

What you really need to know!

Formulas are sets of instructions that need to be followed.

Write the formula.

Replace the variables.

Solve.

Example 1:

If you travel 135 miles in 3 hours, what is your average speed in miles per hour?

d = rt

135 = r(3)

45 = r

45 mph

Example 2:

Find the perimeter of the rectangle.

70 cm15

cm

20 cm

p = 2l + 2w

p = 2•20 + 2•15

Example 3:

The perimeter of a rectangle is 60 feet. Its width is 9 feet. Find its length.

p = 2l + 2w60 = 2l + 2•960 = 2l + 18

Example 3:

The perimeter of a rectangle is 60 feet. Its width is 9 feet. Find its length.

42 = 2l21 = l

21 feet

60 = 2l + 18

a = lw

a = 14•6

a = 84 ft2

Example 4:

Find the area of a rectangle with length 14 feet and width 6 feet.

84 ft26

ft

14 ft Area Demo

Example 5:

The area of a rectangle is 40 square meters. Its length is 8 meters. Find its width.

a = lw40 = 8w5 = w

5 m

Page 133

Guided Practice

#’s 4-9

Pages 131-133 with someone at home and study

examples!

Read:

Homework: Pages 134-136

#’s 10-32 even,

33-34, 38, 40

#’s 44-53Lesson Check CH-3

Page

730

Lesson 3-7

Lesson Check CH-3

Study Guide and Review

Pages

138-140

#’s 1-38(Odd answers in back of book)

Prepare for Test!

Page

141

#’s 1-25

Prepare for Test!

Pages

142-143

#’s 1-19