



So
now multiplying two numbers together is no big deal. 





3
x 4 = 12 
6
x 3 = 18 
5
x 2 = 10 






But
what happens when one or both of the numbers are negative? 





What
would you do with this puppy? 





3
x  4 = ?






Here's
what happens. 


First,
multiply the numbers together. 





We're
multiplying a three and a four together, 


so
we're going to get twelve. 





The
real question is: is it a + 12 or a  12? 


What
does that  in front of the 4 do? 





The
minus goes with the 4. 


It's
called its sign. 





A
number can have one of two different signs, 


positive
+ or negative . 





We
have a special rule that says 


if
the sign of a number is not written, it's positive. 





That
means the 3 has an invisible plus sign. 


The
3 is positive and the 4 is negative. 





Enough
already here's how it works:






When
we multiply two numbers together, 


if
the signs are different the answer is negative. 





If
the signs are the same, 


either
both positive OR BOTH NEGATIVE, 


then
the answer is POSITIVE. 





Read
that again, especially the last part. 


WHEN
WE MULTIPLY, 


IF
BOTH SIGNS ARE NEGATIVE THE ANSWER IS POSITIVE. 





SIGNS
DIFFERENT THE ANSWER IS NEGATIVE






SIGNS
THE SAME THE ANSWER IS POSITIVE






Examples: 





5
x  3 =  15 
Different
signs
makes the answer negative 







6 x 2 =  12 
Different
signs
makes the answer negative 







3 x  4 = 12 
Same
signs
makes the answer positive 






copyright 2005 Bruce Kirkpatrick 
