Different lines of work have different equations that are important. Back in my medical days for instance I was pretty good at quickly taking weight in pounds, converting it to kilograms and calculating doses of medications at milligrams per kilogram.
In my new undertaking, machining, the equation you see below is a biggie. It is how you figure out the RPM setting for lathes and mills. RPM is four times Cutting Speed divided by the diameter of the part you are working on. You can see the Cutting Speeds listed, they vary on the basis of how hard the part is.
Obviously this is important enough to put on the shop wall in gigantic letters. But perhaps this is even important enough that extraordinary measures must be taken to reinforce it. Now, I do try to keep this blog set to high moral standards. But what can I say. You want a class of all guys to think about the diameter and hardness of parts?
Post the equation in the bathroom!