This is introducing a series on useful mental maths that I think it dramatically helps to know. It’s true that in many professions being able to carry out complicated maths isn’t required, however, it’s also true that having some level of numeracy will help in almost all walks of life. I’m going to try and cover some topics I think it would benefit someone to know fluently, something I can’t claim but am working towards. Some of the techniques are more useful than others it is true and so for many people knowing only the most basic ones is all that is required but for those who want to know how to do more I wanted to create a list of things I would love to have found in one place.
Some methods are aimed at being purely mental while others would likely require a pen and paper. The ultimate goal of all of them however should be the former, it should be said though as well that these are methods of approximating and as such are mainly intended for you to be able to get to a reasonably accurate figure relatively quickly. There are many other methods I think are interesting and worth knowing that I will write about but these are often very difficult to do mentally, although I am trying to find good ways of approximating them. Below is a list of the methods I hope I can cover:
- Rule of 72
- Division
- Square roots
- Logarithms
- Approximate geometric mean
- Conjunctive probability
- Kelly Criterion
- Percentages
Neil Hacker 