Addition of signed numbers
You already know that the sum of two positive integers is a positive integer.
The rules below will help you find the sign of the sum of two negative
integers and the sign of the sum of a positive and a negative integer.
Adding Integers with the Same Sign |
To add integers with the same sign, add their absolute values. Give the result the same sign as the integers. |
Adding Integers with Different Signs |
To add integers with different signs, subtract their absolute values. Give the result the same sign as the integer with the greater absolute value. |
Calculate:
a. -16 + (-4)
Add the absolute values.
Give the result the same sign as the integers.
-16 + (-4) = -20 |
b. -30 + 5
Subtract the absolute values.
The result is negative because
|-30|>|5|.
-30 + 5 = -25 |
Addition of several integers
(+2) + (-3) + (-4) = 2 -3 -4 =2 -7 = -5
(-12) + (-4) + (+8) = -12 - 4 +8 = -16 +8= -8