11-6 Multiplying Integers

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Warm UpWarm Up

Lesson PresentationLesson Presentation

Problem of the DayProblem of the Day

Warm UpFind each product.

1. 8 • 4 2. 7 • 123. 3 • 9 4. 6 • 55. 80 • 6 6. 50 • 67. 40 • 90 8. 20 • 700

32 8427

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11-6 Multiplying Integers

30480 3003,600 14,000

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Problem of the Day

Catherine has $14.00 and earns $12.00 for each lawn she mows. If she mows 4 lawns and buys 5 DVDs that cost $11.95 each, including tax, how much money does she have left?

$2.25

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11-6 Multiplying IntegersSkip this one!

Learn to multiply integers.

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11-6 Multiplying Integers

Numbers 3 • 2 –3 • 2

Words 3 groups of 2the opposite of 3

groups of 2

Addition 2 + 2 + 2 –(2 + 2 + 2)

Product 6 –6

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11-6 Multiplying Integers

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Numbers 3 • (–2) –3 • (–2)

Words 3 groups of –2the opposite of 3

groups of –2

Addition (–2) + (–2) + (–2) –[(–2) + (–2) + (–2)]

Product –6 6

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11-6 Multiplying Integers

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Additional Example 1: Multiplying Integers

Find each product.

A. 5 • 2

B. 4 • (–5)

5 • 2 = 10 Think: 5 groups of 2.

4 • (–5) = –20 Think: 4 groups of –5.

To find the opposite of a number, change the sign. The opposite of 6 is –6. The opposite of –4 is 4.

Remember!

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11-6 Multiplying Integers

Write these two examples.

Additional Example 1: Multiplying Integers

Find each product.

C. –3 • 2

D. –2 • (–4)

–3 • 2 = –6 Think: the opposite of 3 groups of 2.

–2 • (–4) = 8 Think: the opposite of 2 groups of –4.

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11-6 Multiplying Integers

Write these two examples.

Check It Out: Example 1

Find each product.

A. 3 • 4

B. 2 • (–7)

3 • 4 = 12 Think: 3 groups of 4.

2 • (–7) = –14 Think: 2 groups of –7.

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11-6 Multiplying Integers

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Check It Out: Example 1

Find each product.

C. –5 • 3

D. –4 • (–6)

–5 • 3 = –15 Think: the opposite of 5 groups of 3.

–4 • (–6) = 24 Think: the opposite of 4 groups of –6.

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11-6 Multiplying Integers

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MULTIPLYING INTEGERS

If the signs are the same, the product is positive.

4 • 3 = 12 –6 • (–3) = 18

If the signs are different, the product is negative.

–2 • 5 = –10 7 • (–8) = –56

The product of any number and 0 is 0.

0 • 9 = 0 (–12) • 0 = 0

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11-6 Multiplying Integers

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Additional Example 2: Evaluating Integer Expressions

Evaluate –7x for each value of x.

A. x = –3

B. x = 5

–7x Write the expression.–7 • (–3) Substitute –3 for x.21 The signs are the same, so the answer

is positive.

–7x Write the expression.

–7 • 5 Substitute 5 for x. –35 The signs are different,

so the answer is negative.

–7x means –7 • x.Remember!

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11-6 Multiplying Integers

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Check It Out: Example 2

Evaluate –4y for each value of y.

A. y = – 2

B. y = 7

–4y Write the expression.

–4 • (–2) Substitute –2 for y.

8 The signs are the same, so the answer is positive.

–4y Write the expression.

–4 • 7 Substitute 7 for y.

–28 The signs are different, so the answer is negative.

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11-6 Multiplying Integers

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Lesson QuizFind each product.

1. 6 • (4) 2. 3 • (–2)

3. –9 • (–2) 4. –6 • 5

5. Evaluate 3y for y = –7.

6. During a football game, Raymond’s team lost 6

yards on each of 3 plays and gained 8 yards on

each of two plays. What integer represents the

total change in the team’s position?

–624

Insert Lesson Title Here

18 –30

–21

–2

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11-6 Multiplying Integers

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