Before leaving the house this morning, a man left this letter for his wife:

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 earn that by the time you receive this letter, I will be at the Grand Hotel with my 18-year old secretary. I'll be home before midnight and will see you then.

Your Husband

When the Husband arrived at the hotel, there was this faxed letter waiting for him:

Dear Husband:

You, too, are 54 years old and by the time you receive this letter, I will also be at the Grand Hotel --- with our 18-year old pool boy.
Since you are an accountant, you will appreciate that 18 goes into 54 many more times than 54 goes into 18. Therefore, don't wait up.

Your Wife