I generally like math jokes; but I came across this one today and I don’t get it.
“What happened to your girlfriend, that really cute math student?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was in bed wrestling with three unknowns…”
The “unknowns” could be three unknown variables in a set of equations, or three unknown people in bed with her.
I think the joke is that the girlfriend, being a math student, meant “unknown variables” while the boyfriend thought she meant “unknown guys”
Three unknowns can be very difficult to solve for, in physics a 3-body problem is often one that must be reduced or simplified in some way before it can be “solved.” So, it’s kind of funny.
But yeah, if you were wrestling with 3 unknowns, it means you’re trying to work with 3 different variables to set up some equations or predict behavior in a system, etc.
Of course, she also could have meant wrestling with 3 unknown people 
Do people really go to bed to solve equations?
No, but if you’re a real math geek you don’t stop solving equations just because you’re in bed.
Reminds me of a joke:
A doctor, a lawyer and a mathematician were discussing the relative merits
of having a wife or a mistress.
The lawyer says: "For sure a mistress is better. If you have a wife and
want a divorce, it causes all sorts of legal problems. "
The doctor says: "It’s better to have a wife because the sense of security
lowers your stress and is good for your health. "
The mathematician says: " You’re both wrong. It’s best to have both so that
when the wife thinks you’re with the mistress and the mistress thinks you’re
with your wife — you can do some mathematics. "
Richard Feynman’s wife included this statement in her divorce complaint
“He begins working calculus problems in his head as soon as he awakens. He did calculus while driving in his car, while sitting in the living room, and while lying in bed at night.”
Dumb math joke if you ask me. (IOW I was reading too much into it)
So there’s nothing special about “3 unknowns?” There’s not some math equation that’s well known with 3 unknowns? The joke would have worked the same with 2 unknowns? I even went so far as to think; “you could specify unknown as x; so is it supposed to be funny because she’s wrestling with 3 x’s?”
Why Did the Chicken Cross the Möbius Strip? To get to the same side.
Now THAT’S a funny math joke!
As usual, there’s an xkcd about that
Well, solving an equation with only one unknown is a piece of cake. Two unknowns is more difficult, but not a major challenge. But a problem with three unknowns is one you’d really have to wrestle with.
Am I the only person who thinks it’s the *other *side of the joke–the non-mathematical meaning–that makes no sense? Why would they be referring to sex partners as “unknowns”?
Ultimately, the meaning is that math enthusiasts should leave comedy to the professionals.
Exactly! To make the joke funny, there has to be a play on words.
It would have been funnier if she was comparing the different circumferences of cylinders of the same volume; i.e. short & thick versus long and thin.
using my example above… wrestling with 3 cylinders of unknown volume is (IMHO) funnier because it makes more sense.
OK, I admit it. I’m kind of pissed off that there was nothing more to the joke. It really was as simple as it seemed. I really wanted there to be some deeper meaning.
“What happened to your girlfriend, that really cute law student?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was in bed wrestling with three briefs”
“What happened to your girlfriend, that really cute electrical engineering student?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was in bed wrestling with three shorts…”
“What happened to your girlfriend, that really cute lifeguard?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was in bed wrestling with three noodles…”
“What happened to your girlfriend, that really cute pasta maker?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was in bed wrestling with three noodles…”
Yeah, about the only way this makes sense if there is a true double meaning, one of which is sexual.
“What happened to your girlfriend, that really cute construction worker?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was at the site nailing three studs”
I believe the better punchline for that is, “… and she told me that she was trying to get a partner’s briefs down.”
That’s a pretty good one, Saint Cad, I think we’re on to something. I’m thinking there are a lot more jokes that could be made in the format of:
“What happened to your girlfriend, that really cute _________?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was insert double meaning phrase hear that relates to the description in the first line”
“What happened to your girlfriend, that really cute accountant?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was inserting a column…”
“double entry” could work somehow too…?
You mean like:
“What happened to your girlfriend, that really cute Jokesmith?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was repeatedly inserting a double entendre”?
Oh, wait, I’ve got one!
“What happened to your girlfriend, that really cute prostitute sidelining as a plumber?”
“She no longer is my girlfriend. I caught her cheating on me.”
“I don’t believe that she cheated on you!”
“Well, a couple of nights ago I called her on the phone, and she told me that she was having multiple-orifice-penetration sexual intercourse with three paying customers at the same time.”