# Primary mathematics/Negative numbers

## Introduction

Negative numbers are numbers less than zero. A convenient way to think of them is as a number owed. For example, if you have negative four apples, that means you owe four apples to someone. A dash is typically used to indicate a negative value. In our case, we would write -4 apples.

## Adding negative numbers

To add two negative numbers, just add normally, then make the result negative:

-4 + -3 = -7

When adding one negative number to one positive number, it can be rewritten as a subtraction problem:

4 + -3 = 4 - 3 = 1

It may be necessary to change the order of the two terms to do this:

-3 + 4 = 4 - 3 = 1

Any subtraction problem can also produce a negative value:

-4 + 3 = 3 - 4 = -1

The last problem can be visualized as if you owed 4 apples, then got 3 (which you gave to the person to whom you owed the apples), so you would still owe them 1 apple.

## Subtracting negative numbers

Subtracting a negative number is the same as adding the same positive number. In other words, two negatives makes a positive:

4 - -3 = 4 + 3 = 7

Or, if both numbers are negative:

-4 - -3 = -4 + 3 = 3 - 4 = -1

## Multiplying negative numbers

Just multiply normally, then apply the following rules:

- If both numbers are negative (or both are positive), the result is positive.

- If only one number is negative, the result is negative.

Thus:

4 × 3 = 12

-4 × -3 = 12

-4 × 3 = -12

4 × -3 = -12

## Dividing negative numbers

Just divide normally, then apply the following rules:

- If both numbers are negative (or both are positive), the result is positive.

- If only one number is negative, the result is negative.

Note that these are the same rules as were used for multiplication:

12 / 4 = 3

-12 / -4 = 3

12 / -4 = -3

-12 / 4 = -3

## Other notations

Negative numbers are sometimes shown in parenthesis, in red, or with DB (for DeBit) next to them, in the field of accounting (that is, when dealing with money).