Multiplication of Real Numbers

Section 2.5

Multiplying Rules1) If the numbers have the same

signs then the answer is positive.

(-7) • (-4) = 28

2) If the numbers have different signs then the answer is negative.

(-7) • 4 = -28

Examples

1) (3x)(-8y)

20 4

5

2) Write both numbers as a fraction.

20

1

4

5

80

5= -16

Multiplying fractions: (multiply across)

-24xy

When multiplying two negative numbers, the product is negative.

1. True

2. False

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When multiplying a negative number and a positive number, use the sign of

the larger number.

1. True

2. False

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2

5

5

8

3)

10

40=

1

4=

Multiply: (-3)(4)(-2)(-3)

1. 72

2. -72

3. 36

4. -36

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Examples:

1.

2.

3. )3)(2

1)(2(

)3(

)3(9

3

What is the sign of the product of (-3)(-4)(-5)(0)(-1)(-6)(-91)?

1. Positive

2. Negative

3. Zero

4. No stinkin’ clue

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