1. multiply rational numbers.
SOL: none
Objective
The student will be able to:
Designed by Skip Tyler, Varina High School and Nicole Kessinger Deep Run High School

2. 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

3. 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

4. −
2
5




−
5
8




3)
10
40
=
1
4
=

5. Multiply: (-3)(4)(-2)(-3)
1. 72
2. -72
3. 36
4. -36
Answer Now

6. 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?

7. 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




120
10

8. What is the sign of the product of
(-3)(-4)(-5)(0)(-1)(-6)(-91)?
1. Positive
2. Negative
3. Zero
4. Huh?
Answer Now