"For all practical purposes" (math humor)

A math professor used the phrase "for all practical purposes" during class. A student asked what he meant by that.

"Suppose we line up all the boys on one side of the classroom and all the girls on the other. On a given signal, both groups will walk half the distance towards the middle of the room. On each subsequent signal, each group will walk half the remaining distance. Theoretically, of course, the two groups will never meet. But in reality, after a few signals, the two groups will be close enough for all practical purposes."

Ethics and ethicists

(From Asimov Laughs Again, Harper Perennial edition 1993, #374, p. 203):

The school year was over and the faculty heaved their usual sigh of relief. Professor Murray of English literature said to his colleague, Professor Cardozo of Romance languages, "I had an interesting experience during the year. A Miss Brentwood came to see me in the middle of the year and said intensely, 'Professor Murray, I'd do anything to get a passing mark in this course, I mean literally anything.' She was a strikingly beautiful girl and I admit I was tempted, but her school record was abominable and I did manage to cling to my integrity. I said, 'Miss Brentwood, I suggest you study.' This, of course, was the last thing she would do and in the end I was forced to give her a failing mark."

"Amazing," said Professor Cardozo, "for precisely the same thing happened to me. I, too, had to flunk Miss Brentwood. Do you suppose she tried it with all her professors?"

"Possibly," said Professor Murray. "Shall we look up her record and see?" 

No sooner said than done. They scanned the record and Professor Cardozo said, "Interesting. An F in my course and in yours and, indeed, in all of them but one. In one course, she got an A."

"And which course was that?"

"Professor Hingman's course in professional ethics."