Rational, << RASH uh nuhl, >> number is any number that can be expressed in the form a/b, where a is any integer and b is any integer except zero. Integers are whole numbers greater than, less than, or equal to zero. Rational numbers include such positive numbers as 3/4 and 2/3 and such negative numbers as –1/3 and –5/2.
Integers are rational numbers because they can be expressed as fractions (a/b). For example, the integers 3 and -5 can be written as the fractions 3/1 and –5/1. Terminating decimals and repeating decimals are also rational numbers. Terminating decimals are decimals that have a limited number of digits. For instance, .75 is a terminating decimal. When expressed in the form a/b, .75 becomes 3/4. Repeating decimals repeat the same digit or a series of digits.
Numbers that cannot be expressed as a/b are called irrational numbers. Pi, for example, can be written as a decimal with an approximate value of 3.14159. However, the decimal continues indefinitely, does not repeat, and cannot be converted into a fraction. Pi is therefore an irrational number.
