11

Bellwork Oct. 7, 2010Evaluate each expression.

1. 17 · 5 2. 8 · 34

3. 4 · 86 4. 20 · 850

5. 275 ÷ 5 6. 112 ÷ 4

85 272

344 17,000

55 28

22

Focus LessonFocus Lesson

-2.4 + 3.6 + 9-2.4 + 3.6 + 9

33

2-4 2-4 Multiplying & Dividing IntegersMultiplying & Dividing Integers

Pg. 94Pg. 94

44

Essential QuestionEssential Question How are multiplying and dividing integers How are multiplying and dividing integers

similar?similar?

55

““Negatives in _______ are __________; Negatives in _______ are __________; ________ in pairs, they’re ________.”________ in pairs, they’re ________.”

““WELCOME TO THE PARTY IN WELCOME TO THE PARTY IN MATHLAND!!”MATHLAND!!”

See if you can fill in the blanks as See if you can fill in the blanks as you listen to the storyyou listen to the story

66

The Party in MathlandThe Party in Mathland

Everyone is happy and having a good Everyone is happy and having a good time (they are ALL time (they are ALL POSITIVEPOSITIVE). ). Suddenly, who should appear but the Suddenly, who should appear but the GROUCHGROUCH (ONE (ONE NEGATIVENEGATIVE)! The )! The grouch goes around complaining to grouch goes around complaining to everyone about the food, music, the everyone about the food, music, the room temperature, the other people.room temperature, the other people.

7777

What happens to the party?What happens to the party?

Everyone feels a lot Everyone feels a lot less happy…the party less happy…the party may be doomed!!may be doomed!!

ONE NEGATIVE MAKES ONE NEGATIVE MAKES EVERYTHINGEVERYTHING NEGATIVE!!!NEGATIVE!!!

88

But wait…is that But wait…is that anotheranother guest guest arriving? What if arriving? What if anotheranother grouch grouch (A (A SECOND NEGATIVESECOND NEGATIVE) appears?) appears?

The 2 negative grouches pair up The 2 negative grouches pair up and gripe and moan to and gripe and moan to each each otherother what a horrible party it is what a horrible party it is and how miserable they are!! But and how miserable they are!! But look!! They are starting to smile; look!! They are starting to smile; they’re beginning to have a good they’re beginning to have a good time themselves!!time themselves!!

9999

Now that the two grouches Now that the two grouches are together the rest of the are together the rest of the people (who were really people (who were really positive all along) become positive all along) become happy once again. The happy once again. The party is saved!!!party is saved!!!

PAIRS OF NEGATIVES PAIRS OF NEGATIVES BECOME POSITIVEBECOME POSITIVE

1100

““Negatives in Negatives in PAIRSPAIRS are are POSITIVEPOSITIVE; ; NOTNOT in pairs, in pairs, they’re they’re NEGATIVENEGATIVE.”.”

1111

So you never get mixed up….So you never get mixed up….

Make a tic tac Make a tic tac toe board……fill toe board……fill it in like this.it in like this.

+ stands for + stands for positive positive numbers, the - numbers, the - for negative for negative numbersnumbers

++ __ __

__ ++ __

__ __ ++

1122

You can think of multiplication as repeated addition.

3 · 2 = 2 + 2 + 2 = 6 and

3 · (–2) = (–2) + (–2) + (–2) = –6

1133

Use a number line to find each product.

Example 1

–7 · 2

+ (–7) + (–7)

–7 · 2 = 2 · (-7)

-14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

–7 · 2 = –14

1144

Multiplication and division are inverse operations. They “undo” each other. Notice how these operations undo each other in the patterns shown.

Remember!

1155

MULTIPLYING AND DIVIDING INTEGERSMULTIPLYING AND DIVIDING INTEGERS

If the signs are: Your answer will be:

the same

different

positive

negative

1166

Find each product.

Example 2

A. –6 · (–5)

–6 · (–5)

30

B. –4 · 7

–4 · 7

-28

1177

Find each quotient.

Example 3

A. 35 ÷ (–5)

35 ÷ (−5)

–7

B. –32 ÷ (–8)

−32 ÷ (–8)

4

1188

Multiplying and Multiplying and Dividing Integers Dividing Integers

Video ClipVideo Clip

1199

PracticePractice

2200

PracticePractice

-10 28

2211

PracticePractice

-8 4

2222

Work SessionWork Session

Textbook Textbook Page 96Page 9618-42 18-42 EVEN ONLYEVEN ONLYGRADEDGRADED

2233

HomeworkHomework

Workbook Workbook Page 16Page 16All problemsAll problemsSTUDY-TEST STUDY-TEST

TOMORROW ON TOMORROW ON INTEGERSINTEGERS

2244

Closing

Find each product or quotient.

1. –3 · 5 · (–2)

2. –75 ÷ 5

3. –110 ÷ (–2)

–15

55

30