Numbers can either be positive or negative. Often brackets are put around negative numbers to make them easier to read, e.g. (-2). If a number is positive, the + is usually missed out before the number. So 3 is really (+3). Adding and multiplying combinations of positive and negative numbers can cause confusion and so care must be taken.

Addition and Subtraction

Two 'pluses' make a plus, two 'minuses' make a plus. A plus and a minus make a minus.

Example

3 + (-2)
A plus and a minus make a minus, so this is the same as 3 - 2 = 1

Example

(-2) + (-5) = -7
This is the same as (-2) - 5 = -7

Multiplication and Division

If two positive numbers are multiplied together or divided, the answer is positive.
If two negative numbers are multiplied together or divided, the answer is positive.
If a positive and a negative number are multiplied or divided, the answer is negative.

Examples

(-2) ÷ (-4) = ½
(8) ÷ (-2) = (-4)
2 × (-3) = (-6)
(-2) × (-2) = 4

Copyright © Matthew Pinkney 2003