Addition with Negative Numbers
1. Rule for adding two numbers that have the same sign: To add two numbers that have the same sign, add their absolute values and use the common sign.
Note: The sum of two positive numbers is a positive number. The sum of two negative numbers is a negative number.
2. Rule for adding two numbers that have different signs: To add two numbers that have different signs, subtract the smaller absolute value from the larger absolute value. The answer will have the sign of the number with the larger absolute value.
Note: The sum of two numbers that have different signs may be positive or negative.
3. Simplifying using the two rules: Identify which rule is to be used, and apply that rule.
Ex: In each of the problems below, identify whether the addition problem is adding two numbers with the same sign or with different signs.
a. 8 + ( -3 ) addition of two numbers that have different signs
b. 6 + 7
c. 6 + (-7)
d. (-3) + (-5)
4. Adding more than two numbers: To add more than two numbers, rearrange the numbers so that all of the positive numbers are first and the negative numbers follow. Then add all of the positives and all of the negatives. Then add the two results.