How do you convert a fraction into an irrational number?

To convert a fraction to an irrational number, you always want the denominator to only contain 9’s, So if the denominator was 33, 33 x 3 = 99, Now multiply the numerator by the same number e.g. 6 x 3 = 18, and divide the numerator by the denominator and write the answer as a recurring number