Decimals (or floating point numbers) are the oposite of fractions, where fractions take the form of a number over a number eg: which is one half.
In decimal format this would be 0.5. Why?
Well one half of 1 is 0.5 since 0.5 * 2 is equal to 1. If we multiply the number at the bottom by the decimal we should get the number at the top. Such as:
Is still one half. since and
So the formulae could be: and thus