Fraction
A fraction is a representation of a rational number, which is written as a division of two numbers
Dividend = Fraction Divisor
Explanation
Many people prefer to write fractions as a decimal number with places after the decimal point. The fraction 
becomes then 0.3. That's inaccurate, because you should write
You can write it as accurate as you want, by repeating the pattern. But what do you do at
That's exact, and does not need to be rounded. Where does the 5 come from? You can indeed convert each fraction to decimal numbers by executing a division.
Conversion
You can not convert every number with decimals to a fraction.
The square root √2 = 1.414213562… cannot be written as a fraction. It is therefore called an irrational number. Eventually there will occur a pattern that repeats itself. The old Greeks, like Pythagoras, did not accept that. They kept it secret, not to worry the people, and continued to seek for a solution.
The number π = 3.1415… cannot be written as a fraction. Particular about this is that there never emerges a pattern that repeats itself. It is therefore called a transcendental number. And there are many such numbers, as e.g. the base of the natural logarithm e = 2.7182…
Conclusion
Learn how to work with fractions.