"Math Knowledge" joke

Two mathematicians were having dinner in a restaurant, arguing about the
average mathematical knowledge of the American public. One mathematician
claimed that this average was woefully inadequate, the other maintained that it
was surprisingly high.
"I'll tell you what," said the cynic, "ask that waitress a simple math question. If she
gets it right, I'll pick up dinner. If not, you do." He then excused himself to visit
the men's room, and the other called the waitress over.
"When my friend comes back," he told her, "I'm going to ask you a question, and I
want you to respond `one third x cubed.' There's twenty bucks in it for you." She
agreed.
The cynic returned from the bathroom and called the waitress over. "The food was
wonderful, thank you," the mathematician started. "Incidentally, do you know
what the integral of x squared is?"
The waitress looked pensive; almost pained. She looked around the room, at her
feet, made gurgling noises, and finally said, "Um, one third x cubed?"
So the cynic paid the check. The waitress wheeled around, walked a few paces
away, looked back at the two men, and muttered under her breath, "... plus a
constant."