The Real Number System

Natural Numbers (AKA Counting Numbers): {1, 2, 3, 4, …}

Whole Numbers (Natural Numbers plus zero):

{0, 1, 2, 3, …}

NOTE: Both of these sets include only positive numbers!

Integers (We now include negative whole numbers): { …-3, -2, -1, 0, 1, 2, 3, …}

Rational Numbers (any number that can be written as a fraction).

This includes all whole numbers, all fractions, and decimals that either terminate or have a repeating pattern.

Irrational Numbers: Numbers that cannot be written as a fraction. These are certain types of square roots (√2) and numbers like π. Both of these are decimals that never end and never repeat.

Empty set: { } Means there are no values in the set.

1) ¾ is an integer. 2) √3 is a real number. 3) 9.2 is a rational number. 4) Every counting number is a rational

number. 5) -2 ½ is a rational number. 6) 0 is not a positive number.