Rational Numbers

A Rational Number is a real number that can be written as a simple fraction (i.e. as a ratio).

Example:

1.5 is a rational number because 1.5 = 3/2 (it can be written as a fraction)



Here are some more examples:

Number As a Fraction    Rational?
5 5/1 Yes
1.75  7/4 Yes
.001 1/1000 Yes
-0.1 -1/10 Yes
0.111... 1/9 Yes
√2 
(square root of 2) ? NO !
Oops! The square root of 2 cannot be written as a simple fraction! And there are many more such numbers, and because they are not rational they are called Irrational.

Another famous irrational number is Pi (π)