GED LESSON: Pre-Algebra: Adding and Subtracting Negative Numbers

ADDITION WITH NEGATIVE NUMBERS 


When adding numbers with the same signs (the signs of both numbers are positive or the signs of both numbers are negative),

Adding numbers with SAME SIGNS

1. Add the numbers
2. The answer keeps the same sign

For instance:      

         +2  +  +7  = +9
         -2  +  -7  = -9

When adding numbers with the different signs (if the first number is positive and the second number is negative, or the first number is negative and the second number is positive)

Adding numbers with DIFFERENT SIGNS

1. SUBTRACT the smaller number from the larger number regardless of signs)
2. Get the answer
3. Apply the sign of the larger number to the answer.

For instance:

         +2  +  -7  =  

          Step #1: Subtract the smaller number (2) from (7): 7 - 2 = 5 
          Step #2 The answer is 5
          Step #3 Since 7 is larger than 2 and 7 is negative, turn 5 into negative 5, so
       -5 is the answer. 

+2  +  -7  = -5

SUBTRACTION WITH NEGATIVE NUMBERS 

Subtraction is easy. Just change the sign of the SECOND number, then ADD using the additions rules above.

Examples:

Example one:           +2  -  -7  = +2  +  +7 = +9

Example two:           -2  -  +7  = -2  +  -7  = -9

Example three:               +2  -  +7  = +2  +  -7 = -5 

Example four:               -2  -  -7  = +2  +  +7 = +5 

FURTHER EXPLANATION AND PRACTICE CLICK HERE

GED LESSON: Negative Numbers (SuccessGED)

From Wikipedia

In mathematics, a negative number is a real number that is less than zero. Negative numbers represent opposites. If positive represents movement to the right, negative represents movement to the left. If positive represents above sea level, then negative represents below level. If positive represents a deposit, negative represents a withdrawal. They are often used to represent the magnitude of a loss or deficiency. A debt that is owed may be thought of as a negative asset, a decrease in some quantity may be thought of as a negative increase. If a quantity may have either of two opposite senses, then one may choose to distinguish between those senses—perhaps arbitrarily—as positive and negative. In the medical context of fighting a tumor, an expansion could be thought of as a negative shrinkage. Negative numbers are used to describe values on a scale that goes below zero, such as the Celsius and Fahrenheit scales for temperature. The laws of arithmetic for negative numbers ensure that the common sense idea of an opposite is reflected in arithmetic. For example, − − 3 = 3 because the opposite of an opposite is the thing you started with.

Negative numbers are usually written with a minus sign in front. For example, −3 represents a negative quantity with a magnitude of three, and is pronounced "minus three" or "negative three". To help tell the difference between a subtraction operation and a negative number, occasionally the negative sign is placed slightly higher than the minus sign (as a superscript). Conversely, a number that is greater than zero is called positive; zero is usually^[1] thought of as neither positive nor negative.^[2] The positivity of a number may be emphasized by placing a plus sign before it, e.g. +3. In general, the negativity or positivity of a number is referred to as its sign.

Every real number other than zero is either positive or negative. The positive whole numbers are referred to as natural numbers, while the positive and negative whole numbers (together with zero) are referred to as integers.

In bookkeeping, amounts owed are often represented by red numbers, or a number in parentheses, as an alternative notation to represent negative numbers.