A college math professor and his wife are both 60 years old. One evening the wife comes home and finds a note from her husband that says, "My dear, now that you are 60 years old, there are some things you no longer do for me. I am at the Holiday Inn with my 20-year-old student. Don't bother waiting up for me."
He returns home late that night to find a note from his wife: "You, my dear, are also 60 years old and there are also things I need that you're not giving me. So I am at the Motel 6 with one of your 20-year-old students. Being a math professor, I'm sure you know that 20 goes into 60 way more than 60 goes into 20. So, don't you wait up for me."

OMG!

Love this one.

I like the way you use the biblical euphemism "goes into" but I doubt if the Sunday school teacher would use this story to explain the meaning of the term.

Well, as long as they are both happy, it's a good thing, right?

I don't understand why he came home at all.

He had to! 60 doesn't go into 20 that many times.

Actually, the joke doesn't say he did come home.

Even the reaction / responses to the joke are funny.

I agree... Sometimes that is why I come in and read the jokes..