multiply rational numbers.

SOL: none

ObjectiveThe student will be able to:

Designed by Skip Tyler, Varina High School and Nicole Kessinger Deep Run High School

Multiplying Rules

1) If the numbers have the same signs then the product is positive.

(-7) • (-4) = 28

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

(-7) • 4 = -28

Examples

1) (3x)(-8y)

20 4

5

2) Write both numbers as a fraction.

Cross-cancel if possible.

20

1

4

5

80

5= -16

Multiplying fractions:

top # • top #

Bottom # • bottom#

-24xy

2

5

5

8

3)

10

40=

1

4=

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

1. 72

2. -72

3. 36

4. -36

Answer NowAnswer Now

an easy way to determine the sign of the answer

3 negative signs -> Odd -> answer is negative-480

When you have an odd number of negatives, the answer is negative.

When you have an even number of negatives, the answer is positive.

4) (-2)(-8)(3)(-10)Do you have an even or odd number of

negative signs?

Last one!

5) 1

2

6 5 2

5

2

Positive or negative answer?Positive - even # of negative signs (4)

Write all numbers as fractions and multiply.

=12

1

2

6

1

5

1

2

5

2

1

12010

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

1. Positive

2. Negative

3. Zero

4. Huh?

Answer NowAnswer Now