I try to think about whether two concepts are innately similar or incidentally similar. Computing compounding interest for a home equity loan and a mortgage might be innately similar. A desired change to one will probably make a desired change to the other. Computing growth of a fruit fly population and computing compounding interesting for a loan might be incidentally similar. Until you change your "computeExponentialGrowth" function to now handle occasional decimations from environmental sources, and anyone looking at the code wonders what the heck that looks like for a loan.