After a lengthy summer break, students' reasoning skills may be a little rusty. So a logical analysis of some commonplace sayings may be just the thing to exercise those mental muscles.
For example, at school, every student will hear that "knowledge is power", and the first time they show up late to work, their boss will lecture that "time is money." Moreover, in physics class, the professor will inform them that work is just power multiplied by time.
So if they combine all of this wisdom and make a few simple substitutions, then they will discover that work is the product of knowledge and money. But that just means that for any given job, as your knowledge goes to zero, then the money you will make becomes infinitely large. So, ummm ... it seems that I've made a horrible, horrible mistake. Let's just agree that this logic exercise is stupid -- but then according to our previous reasoning, that makes it very valuable.