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Transcript
```Objective
The student will be able to:
multiply rational numbers.
SOL: none
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)
-24xy
2)
4 

20 
5
Write both numbers as a fraction.
Cross-cancel if possible.
 20 4 
 1 5 
Multiplying fractions:
80

5
top # • top #
= -16
Bottom # • bottom#
When multiplying two negative
numbers, the product is negative.
1. True
2. False
When multiplying a negative number
and a positive number, use the sign of
the larger number.
1. True
2. False
2
5




3) 

 5  8 
10
=
40
=
1
4
Multiply: (-3)(4)(-2)(-3)
1.
2.
3.
4.
72
-72
36
-36
an easy way to determine the sign of the answer
When you have an odd number of negatives,
When you have an even number of negatives,
4) (-2)(-8)(3)(-10)
Do you have an even or odd number of
negative signs?
3 negative signs -> Odd -> answer is negative
-480
Last one!
1
2



2
5)  65
 2 
 5 
Positive - even # of negative signs (4)
Write all numbers as fractions and multiply.
 1  6 52  2 
 2  1 1  5  1 
120
10
=12
What is the sign of the product of
(-3)(-4)(-5)(0)(-1)(-6)(-91)?
1.
2.
3.
4.
Positive
Negative
Zero
Huh?