This is a common expression used, but it may not be known by those who are new Canadians. Which is why I thought it would make sense to post this factfulness poster.
In essence, a rule of thumb is a general way of following a practical and logical path. It is used to take a complex problem and allow you the opportunity to break it down and find the solution. I have never seen all of these methods in one place, and each one is extremely valuable to learn.