Mr. Lake's Math Site

Positive and Negative Numbers

​Adding and Subtracting

• If they are the same sign, then we add them and keep the sign
  
• If they are different signs, then we subtract them, and whatever we have more of is the sign of our answer.
  

example: 

2+5=7  They have the same sign, so we just add.

-3+-7=-10 These also have the same sign, so we add and keep the sign.

5+-8=-3  Here the signs are different so we subtract, and since we have more negatives here, then the sign of our answer is negative.

Sometimes the way they are written can be confusing, so it is important to understand that

5-8

5+(-8)

5+-8

are all the same.

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