Arithmetic/Types of Numbers

We can classify numbers into several different kinds.

Natural number

The natural numbers are those that children first learn about, the positive whole numbers used for counting, i.e. 1, 2, 3, 4.....

Whole number

A whole number is a number that is either a natural number or zero.

odd number =2n-1  even number=2n

Integer

An integer expands the set of whole numbers by including numbers less than zero (or negative numbers). Thus integers are the numbers ...-2, -1, 0, 1, 2...

[[Media:File:Example.ogg

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]]=== Negative Numbers === the negative numbers are written with a -on the left side

-10-9-8-7-6-5-4-3-2-1 0 1 2 3 4 5 6 7 8 9 10

Rational number

A rational number is a number which can be written in the form of one integer divided by another or A/B. For technical purposes, A and B must be relatively prime (only common factor between A and B is 1). All integers are rational since they can all be expressed as the integer divided by one.

Irrational number

An irrational number is a number which is not a rational number. Examples of irrational numbers include $\sqrt{2}$ and $\pi$.

Real number

Real numbers include all rational and irrational numbers. The real numbers form the continuous 'real line' of numbers.

Complex number

Complex numbers are of the following form: z = a + bi where: a and b are real numbers and i is the 'imaginary unit' $\sqrt{-1}$.