Positive And Negative Review

Positive and Negative Review p.778-783 By Robert C. Gonzalez CE Instructor, San Antonio College

Three categories of positive and negative problems:
Add and Subtract  Ex: -5+2= -3, -8-4= -12, -9+12= 3


Double Signs (a combination between Add and Subtract and Multiply/Divide)  Ex: 8-(+5)= 3, 2-(-4)= 6, 8++5= 13


Multiply and Divide  Ex: -5*3= -15, -10/2= -5, -3(-3)= 9

General Steps
Figure out which of the three categories the problem is in. (Add/Subtract, Double Sign, or Multiply/Divide)
Identify if the numbers have the “same signs” or “different signs”.  “same sign” means ALL positive or ALL negative.  “different signs” mean there is a mix of positive and negative numbers in the problem.
Use the correct method.  The method will depend on whether or not the numbers have the “same” or “different” signs and what category the problem is in.

Add and Subtract SAME signs

DIFFERENT signs


Add all the numbers and keep the sign.


Subtract all the numbers and keep the sign of the “bigger number”

“bigger number” is an oversimplified way to say “the number with the largest absolute value”.

Double Sign rule SAME + + or - -

DIFFERENT + - or - +


Change double sign into a “+” (plus sign)


Change double sign into a “-” (subtraction sign)

Multiply and Divide SAME Neg * Neg = Positive Pos/ Pos = Positive

DIFFERENT Neg * Pos = Neg Neg/Pos = Neg