An old anecdote from my alma mater – in an introductory course to discrete math, the professor was teaching combinatorics and began: “Suppose you have an urn with three balls inside colored red, green and blue…” At this point one of the students interjected: “Half the class are electrical engineering majors, how is any of this relevant to our studies?” there was a beat and the professor corrected himself: “Suppose you have an urn with three resistors inside colored red, green and blue…”