A fraction can be changed into a decimal by dividing the numerator by the denominator. You can use a calculator, or see how to do it in the following window.

The result could be:

1.- A WHOLE NUMBER.- For example: 72/9=8. This is the case when the numerator is a multiple of the denominator.
2.- A TERMINATING DECIMAL. - For example: 197/40=4.925. This is the case when the numerator is multiplied by a power of 10 as the result is an exact multiple of the denominator.

3.- A PURE RECURRING DECIMAL - For example: 4/11=0.36363636... The decimal numbers form a pattern that is repeated indefinitely after the decimal point. 
4.- A MIXED RECURRING DECIMAL.- For example: 87/66=1.3181818... The first decimal(s) after the decimal point are not repeated, but the subsequent numbers form a pattern which is repeated indefinitely, as in the previous example.

Look at these different examples in the window.

Therefore, we could say that any fraction can be expressed as a recurring decimal. We can also say that the opposite is true, i.e. that any recurring decimal can be expressed as a fraction. From now on we shall refer to these numbers as rational numbers.

To sum up:

ANY NUMBER THAT CAN BE EXPRESSED AS A FRACTION IS KNOWN AS A RATIONAL NUMBER

We have just seen how we can get four different types of numbers when we divide a fraction. All of these numbers are RATIONAL. We are going to refer to this group of numbers with the letter Q.