The set of rational numbers
includes all numbers that can be expressed as one integer
divided by another integer, also known as a common
fraction. The term rational comes from the word ratio.
A ratio is the comparison of one number over another number through division.
When writing rational numbers in decimal form they yield a decimal
fraction which has a finite decimal part or an
infinitely repeating decimal part. For example, one
eighth equals .125 which is finite, and one-third equals .33333. . ., which
repeats infinitely. The set of rational numbers includes the set of integers
and the set of natural numbers. A rational number
can be a negative number or a positive number. It
is a proper subset of the entire set
of real numbers. The set of real numbers also includes irrational
numbers. Within the set of rational numbers the arithmetic functions
of addition, division, multiplication
and subtraction will lead to another rational number.