Page 40 - Math Course 2 (Book 1)

Algebraic Equations: Use Formulas

Mo. 1

Lesson 9 Key Concept

Perimeter of a
KEY CONCEPTS: Rectangle
1. Solve problems by using formulas.
2. Solve problems involving the perimeters Words The perimeter of a rectangle is twice the
sum of the length and width.
and areas of rectangles.
Symbols P = + + w + w
P = 2 + 2w or P = 2( + w)
MO. 1 - L9a
Model
Solve Problems By Using w

Formulas

Vocabulary A-Z Area of Rectangle
Let us learn some vocabulary
Words The area of a rectangle is the product
of the length and width.

Symbols A = w
Formula
Model
is an equation that shows a relationship among
certain quantities. w

d = rt, which shows the relationship between
distance d, rate (or speed) r, and time t.

Perimeter

The distance around a geometric f gure is called the Let’s Begin
perimeter.

W P = 2 + 2W Real World Example

TRAVEL
If you travel 135 miles in 3 hours, what is your
average speed in miles per hour?
Area Method 1 Substitute f rst.

The measure of the surface enclosed by a f gure is
its area. d = rt Write the formula.

135 = r • 3 Replace d with 135 and t with 3.

135
W A = x W = 135 Divide each side by 3.
3 3
45 = r Simplify.

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