A week later, the math professor calls him: "I'm sorry, but your equations are complete nonsense." The physics professor is, of course, disappointed. Strangely, however, his incorrect equations turn out to be surprisingly accurate in predicting the results of further experiments.

So, he asks the mathematician if he was sure about the equations being completely wrong. "Well", the mathematician replies, "they are not actually complete nonsense. But the only case in which they are true is

A: Because Oct 31 = Dec 25.

To his surprise, the auditorium is crammed when his talk begins. After he has finished, someone in the audience raises his hand.

"But you said nothing about the actual topic of your talk!"

"What topic do you mean?"

"Well, the one that was announced in the paper: Convicts, sex, and inequality."

"There is one final piece of advice I'm going to give you now: Whatever you have learned in my course - never ever try to apply it to your personal lives!"

"Why?" the students ask.

"Well, some years ago, I observed my wife preparing breakfast, and I noticed that she wasted a lot of time walking back and forth in the kitchen.

So, I went to work, optimized the whole procedure, and told my wife about it."

"And what happened?!"

"Before I applied my expert knowledge, my wife needed about half an hour to prepare breakfast for the two of us. And now, it takes me less than fifteen minutes..."

"Where did you get the bike from?" his friends want to know.

"It's a `thank you' present", he explains, "from that freshman girl I've been tutoring. But the story is kind of weird..."

"Tell us!"

"Well", he starts, "yesterday she called me on the phone and told me that she had passed her math final and that she wanted to drop by to thank me in person. As usual, she arrived at my place riding her bicycle. But when I had let her in, she suddenly took all her clothes off, lay down on my bed, smiled at me, and said: "You can get from me whatever you desire!"

One of his friends remarks: "You made a really smart choice when you took the bicycle." "Yeah", another friend adds, "just imagine how silly you would have looked in a girl's clothes - and they wouldn't have fit you anyway!"

"You know", the son explains, "when I walked into the classroom the first day, and I saw that guy on the wall nailed to a plus sign, I knew one thing: This place means business!"

When the conference actually takes place, he speaks about something completely different. After his talk, a colleague asks him: "Did you find an error in your proof?"

He replies: "No - I never had one." "But why did you make this announcement?"

"That's my standard precaution - in case I die on my way to the conference..."