Here's the secret to adding integers: one positive and one negative added together cancel each other out.
Think about it like this, if you bonk your sister on the head (a negative), then you give her a hug (a positive), your actions cancel each other out. Neutral. Neither bad nor good. (Don't try this at home!)
Let's try it as pictures: In this section we will use symbols (+) and (-) to represent each problem.
For the problem
Five minuses and seven pluses. Each pair of plusses and minuses cancels out.
There are two + left, representing the answer +2.
Use the number line below to solve .
Start at and jump places in the positive direction (to the right). You'll land on the answer, .
Look Out: sometimes you may see parentheses around negative numbers. These do not mean that we need to multiply; they are just used so that we don't confuse negatives with subtraction.
Start at –3. Jump 2 places in the negative direction. You land on the answer, –5. | Start at –4. Jump 3 places in the positive direction. You land on the answer, –1. |
Start at +2. Jump 2 places in the negative direction. You land on the answer, 0. | Start at +4. Jump 1 place in the negative direction. You land on the answer, +3. |
Rule #1: If the signs are the same, add the two numbers together and keep the same sign
Rule #2: If the signs are different, subtract the two numbers and keep the sign of the number with more