Answer: A surprise quiz

The next week Joe Math bet a small fraction of a point that the quiz will be on Monday. He lost. He then bet 10 times that amount on Tuesday. That way if we won he would have covered his loss and in fact be little bit ahead. He lost again. But, on Wednesday, after increasing his yet again he won. Coming out positive on betting for the week.

The professor, who had run out of charity, since Joe hadn't turned in the first assignment nor obviously done the reading, gave him a zero on the quiz.

For the next few weeks, this was the pattern of things. Each Monday a small bet was placed. As it got closer to Friday, if no quiz had been given the bet was increase. In this fashion, Joe Math managed to end each week with more points than he started. But, he kept getting zeros on the quizzes and not turning in the weekly assignments.

The professor decided it was time for a meeting. He wrote the dreaded "See me." on Joe's latest quiz.

Joe gathered up all his quizzes and brought them along with him to his meeting with the professor.

The professor said, "At this rate you won't be passing this semester." To which Joe readily agreed. "In fact, you won't be passing next semester either unless you start doing some of the work." Again Joe agreed, but much to the annoyance of the professor, he didn't look at all sheepish. The professor in exasperation finally said, "When exactly do you plan on passing this course?"

To which Joe replied, "Oh, maybe in ten thousand years."


Joe continued, "As you have probably noticed I've made points in the betting each week. Not a lot, but a small amount. If I keep plowing those points back in to the next weeks bet, that amount will start growing exponentially. Not at a very fast rate, but exponential growth is a wonder to behold. Eventually, I'll be making millions of points per week. At that point, I'll be able slowly make up for all those years of earning nothing on each quiz and nothing on each homework and nothing on each exam. I figure in less than 10,000 years (few if I can take summer school) I should have accumulated an average over 105%. So, it looks to me like I'm cruising for an A+."

The professor pauses in though for a few minutes. It isn't the math that is confusing him, but instead it is the implications about definitions of knowledge. With a start, he comes back to the present moment and says, "OK, I get your point. But that is a long time to wait. Your younger than I, but even 12 year olds don't live that long."

Joe eyes light up, "Oh, I think I'll be happy with an A."

The professor, who actually does have a mind like a steal trap, gets right to the point, "Do I recall correctly that I wrote something like 'You will have to study if you want to pass this course' on your first quiz?"


"Bummer. You've got your A. That is unless you prefer to wait around for your A+ to materialize."

"No, I plan on finishing my Ph.D. next year."

"Want to bet on that?"

David Lischka came up with basically the same solution.

Last modified: Tue Jun 10 10:34:04 EDT 2003