A professor of mathematics sent a fax to his wife. It read:

Dear wife,

You must realize that you are 54 years old, and I have certain needs
which you are no longer able to satisfy. I am otherwise happy with
you as a wife, and I sincerely hope you will not be hurt or offended
to learn that by the time you receive this letter, I will be at the
Grand Hotel with my 18-year old teaching assistant.

I'll be home before midnight,

Your Husband.


When he arrived at the hotel, there was a faxed letter waiting for
him that read as follows:

Dear Husband,

You, too, are 54 years old, and by the time you receive this letter,
I will be at the Breakwater Hotel with the 18-year-old pool boy.
Being the brilliant mathematician that you are, you can easily
appreciate the fact that 18 goes into 54 a lot more times than 54
goes into 18.

Don't wait up,

Your Wife.