Law of multiple proportions is illustrated by the following pair of compounds

Example for law of multiple proportions 

The ratio means that for nitrogen monoxide (NO), for every 1g of nitrogen, there is 1.143g of oxygen. For nitrogen dioxide (NO₂) for every 1g of nitrogen there is 2.286g of oxygen. 
When two elements combine to form two or more than two compounds, the weight of one of the element which combine with a fixed weight of other bear a simple whole number ratio. 
$\therefore$ Ratio of oxygen is different compounds which combine with same of weight of nitrogen is  

$16:32\Rightarrow 1:2$
Hence law of multiple proportions is verified.