Oh, you mean like TSA employees who can't tell the difference between ounces used to measure mass and ounces used to measure volume?

Or TSA employees who can't seem to distinguish between "3 oz", "3.0 oz", "3.4 oz", and "100 ml"?

Regrettably, there's no lack of innumeracy among us. As I tell my students, there are three types of people: those who can count and those who can't.

(wait for it ...)