I really learned fractions by learning to cook. I still use a lot of what I learned in school for halving or doubling a recipe. Of course, it's always nice to have that tool in an online recipe so I can specify the number of servings I want and have the converter do the fractions for the recipe.
Of course, a denominator is also the one something a number of different things have in common with each other. Police officers use this process all the time in solving murders. It's easier to solve a puzzle when you know the one common feature everything has.