1. The Real Number System

2.  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!

3.  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.

4.  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.

5. Real Numbers Rational Numbers Integers Negative Integers Whole Numbers Zero Natural Numbers Non-integers Irrational Numbers

6.  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.