Pre Algebra (Period 2 & 4)

Multiplying & Dividing Integers 1-9

They have the SAME rules!!!!

Math Book Rules:
If you have 2 signs that are the SAME -
answer is POSITIVE
If you have 2 signs that are DIFFERENT -
answer is NEGATIVE

Good Guy/Bad Guy Rules:
GOOD thing happens to GOOD person= GOOD = POSITIVE

BAD thing happens to BAD person = GOOD = POSITIVE
(they got what they deserved!)

GOOD thing happens to a BAD person = BAD = NEGATIVE
(we hate when good things happen to people who don't deserve it!)

BAD thing happens to a GOOD person = BAD = NEGATIVE
(we hate when that happens because it's so UNFAIR!)

Finger Rules:
If your index finger represents the negative sign, then if you have 2 negatives, you have the index fingers of both your left hand and your right hand and they make a plus sign!
If you just have one negative, it just stays negative because you don't have another finger to cross it!
If you have more than 2 negatives, you just keep using your index fingers to determine the sign.
We did this in class. It's fun! But once you get it, you won't need to keep doing it! (unless you want to keep having fun!!!)

WHAT IF THERE IS MORE THAN 2 SIGNS?
Use Aunt Sally Rules and go left to right
or
BE A SIGN COUNTER:
an ODD number of NEGATIVES = NEGATIVE
an EVEN number of NEGATIVES = POSITIVE

EXAMPLE: (-2) (-5) (-3) = -30 (odd number of negatives)
(2) (-5) (-3) = +30 (even number of negatives)
(2) (5) (-3) = -30 (odd number of negatives)

Averages ( or the Mean): Adding up all the numbers and dividing by the number of numbers

Add all the numbers
by the # of #'s


-27 + -27 + -26 + -28 +-32
- 54 + -26 + - 60
-80 + -60 = -140

then divided -140/5 = -28



-3, 4, 2, 1, -4, -1, 3, -2
cross off the zero pairs

0/8 = 0

Then we look at some cold temperatures and figured the average temperature
-9, - 12, 9 4, -2

crossed out zero pairs the numbers add to -10

so average -10/5 = -2 degrees