Most modern cryptography is based on the fact that it's easy to multiply large numbers together, but very difficult to factor the result. This makes it possible to easily encode messages, but almost impossible to decode them without the key. That principle is what allows us to keep so much information (bank records, etc.) online without worrying that it will be stolen.Real life is vast and you do not know all the problems you will encounter. Probably not the answer you wanted, but the truth is if you are learning something new, you do not necessarily know where the skill will lead you. Factoring is a basic skill that will eventually become second nature and you will not even notice that you are factoring in order to simplify seemingly complicated problems. 
As a more simple answer, any time you scale something you are taking a multiple of the original.please mark as best