Here's the thing about calculation in particular: Yes, if your ultimate goal is to perform the calculation and nothing more, you'll be able to use a tool for th

Here's the thing about calculation in particular: Yes, if your ultimate goal is to perform the calculation and nothing more, you'll be able to use a tool for the job in the real world. However, many times the calculation is just a very small piece of a much larger puzzle. In such situations, being able to perform small computations rapidly in your head makes a qualitative difference that can really give you a competitive advantage.