Lesson Quiz

Lesson Presentation

Lesson 3.5Solving Inequalities Using Multiplication or Division

Skill Check

Skill Check

2. 85 ÷ (-5) =

3. -7 • (9) =

-32

-17

-63

1. 4 • (-8) =

4. -39 ÷ (-3) = 13

Evaluate.

Vocabulary Is a mathematical statement

formed by placing an inequality symbol between two expressions. Symbols are: <, >, <, >

With a variable is the set of all numbers that produce true statements when substituted for the variable.

Are inequalities that have the same solution.

Study Strategy

Solving inequalities is the same as solving equations except that when you multiply or divide by a negative number the symbol is reversed.

Solving an Inequality Using MultiplicationEXAMPLE 1

SOLUTION

a. k ÷ -8 > -5

Solve.

a. k ÷ -8 > -5

k < 40 y > 78

b. y ÷ 6 > 13 c. m ÷ -4 < 15

b. y ÷ 6 > 13c. m ÷ -4 < 15

m > -60

40 0

78 0

-60 0

Solving an Inequality Using DivisionEXAMPLE 2

SOLUTION

a. -18y < 72

Solve.

a. -18y < 72

y > -4 f < 28

b. -2f > -56 c. 7m < -147

b. -2f > -56c. 7m < -147

m < -21

-4 0

28 0-21 0

Writing and Graphing an InequalityEXAMPLE 3Customer Service On average, Kevin a customer service representative helps at most 160 customers during an 8-hour workday. Write and solve an inequality to find the average number of customers c he can help each hour during one of his workdays. Write a verbal model, then graph the inequality.

ANSWER

c < 20 20 0

Kevin helps each hour-customers c

<Kevin’s average number of customers

÷8 hour workday

c < 160 ÷ 8

Kevin can help 20 or fewer customers on average each hour during one of his workdays.

Lesson Quiz

1. 14m > -56

2. a ÷ -3 < 9

3. Write the following verbal sentence as an inequality. Then solve the inequality. Six times a number is no more than -96.

m > -4

a > -27

6n < -96

Solve the Inequality. Graph your solution.

4. Challenge Christina is ordering gimbop for her classmates. They cost 2250 won each, including tax, and there is a 6000 won delivery charge. How many gimbops can she buy if she has 42000 won?

-27 0

-4 0

n < -16

2250g + 6000 < 42000

g < 16

She can buy at most 16 gimbops

Closure• 1.) When does an inequality symbol

need to be reversed when solving an inequality.

Whenever each side of the inequality is multiplied or divided by a negative number

Closure• 2.) If 0 < a < b, which is greater, a/b or –b/-a?

-b/-a

Lesson 3.5 Homework:pp.148-150 Exs. (11, 22, 24, 26, 30, 32, 34, 36, 38, 59, 60, 61)Challenge/Bonus Question 49