Adding & Subtracting Positive and Negative Numbers

When you add positive and negative numbers it can be confusing trying to figure out if the answer should be positive or negative. Before we go over two shortcuts for adding negative numbers, let’s look at two visual examples that illustrate what is happening when adding these numbers.

When you add a positive number on a number line you move to the right. You start at the first number, and move to the right.

For example 4+5
Start at 4 and move 5 places to the right, which equals 9

-6 + 8
Start at -6 and move 8 places to the right, which equals 2

When you add a negative number, you do the opposite. You move to the left on the number line.

4 +(-6)
Start at 4 and move 6 places to the left, which equals -2

-1 +(-3)
​Start at -1 and move 3 places to the left, which equals -4

You can use coins to illustrate how to add a positive and negative number

Adding Negative Numbers

Shortcut for Adding Negative Numbers

1. When adding sign numbers with the same sign, you add the numbers, and keep the same sign.

For example:

3+3= 6

-4+-3= -7

2. When you have different signs, you subtract and keep the sign of the number you have “more” of.

For example:

-7 +3 = -4 ( you have more -7’s than 3’s )

-4 + 8 = 4 ( you have more 8’s than -4’s)

Adding Negative Numbers Chart

(+) + (-) = Take the sign of the largest number

(-) + (-) = –