Rules for multiplying/dividing integers (these should be in your notes):
(Please note that while all these examples include multiplication, the same rules apply to division.)
* When multiplying or dividing, if both numbers have the same sign, the answer is positive. *
Examples:
6 x 5 = 30 ---> Both 6 and 5 have the same sign (they're positive). The answer is positive.
-7 x -3 = -21 ---> Both -7 and -3 have the same sign (they're negative). The answer is positive.
* When multiplying or dividing, if the two numbers have different signs, the answer is negative. *
Example:
-4 x 8 = -32 ---> -4 and 8 have different signs (one is positive, the other negative). The answer is negative.
Some reminders for multiplying or dividing with more than two integers - you have two options:
1. Use order of operations to do one operation at a time. Example (remember that numbers in parentheses with no operations next to each other means multiply!):
-3(2)(-5) ---> Multiply left to right. Start with -3 x 2.
-6(-5) ---> Negative x negative = a positive.
= 30
OR
2. Use the following rule:
When solving multiplication or addition for more than two numbers, an even number of negatives gives a positive answer. An odd number of negatives gives a negative answer.
Examples:
-4(3)(-2)(-1)(-2) ---> I see an even number of negative numbers (4 of them) - positive answer!
= 48
2(-3)(-5)(1)(-4) ---> I see an odd number of negative numbers (3 of them) - negative answer!
= -120
