A professor of mathematics sent a fax to his wife. It read:
"Dear wife, You must realise 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.
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, I will be at the Breakwater Hotel with the 18-year-old car wash 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!