What does decimal notation mean in math?

Answer 1

It means that a number expressed as a decimal notation isn't being expressed as a fractional notation. 0,25 and 1/4. ( Both represent the same)

(It's easier to work on fractional notation although the results are the same.)

5/165 = 0,0303030303030303030303030303030.....................

In this example the decimal notation has an infinite length, but you can cut the unnecessary decimal figures= 0,030