You are Visitor

 Contact Us

Phone: 718-745-2370

Fax: 718-680-6770

E-mail: info@streamlineschool.org

Mathematical Jokes

  lim sin(x) /n  = 6, when n -->oo (infinity)

Proof: Cancel the n in the numerator and denominator and remove the parenthesis from x. 

A somewhat advanced society has figured how to package basic knowledge in pill form.

A student, needing some learning, goes to the pharmacy and asks what kind of knowledge pills are available. The pharmacist says "Here's a pill for English literature." The student takes the pill and swallows it and has new knowledge about English literature!

"What else do you have?" asks the student.

"Well, I have pills for art history, biology, and world history," replies the pharmacist.

The student asks for these, and swallows them and has new knowledge about those subjects.

Then the student asks, "Do you have a pill for maths?"

The pharmacist says "Wait just a moment", and goes back into the storeroom and brings back a whopper of a pill and plunks it on the counter.

"I have to take that huge pill for maths?" inquires the student.

The pharmacist replied "Well, you know maths always was a little hard to swallow."

• What's the contour integral around Western Europe?
  Answer: Zero, because all the Poles are in Eastern Europe!
  Addendum: Actually, there ARE some Poles in Western Europe, but they are removable!
• An English mathematician (I forgot who) was asked by his very religious colleague: Do you believe in one God?
  Answer: Yes, up to isomorphism!
• What is a compact city?
  It's a city that can be guarded by finitely many near-sighted policemen!

Moebius always does it on the same side.

Statisticians probably do it

Algebraists do it in groups.

(Logicians do it) or [not (logicians do it)].

((12 + 144 + 20 + (3 * 4^(1/2))) / 7) + (5 * 11) = 9^2 + 0

Or for those who have trouble with the poem:

A Dozen, a Gross and a Score,
plus three times the square root of four,
divided by seven,
plus five times eleven,
equals nine squared and not a bit more.

("The Lure of the Limerick" by W.S. Baring-Gould, p.5. Attributed to Harvey L. Carter).

Shift to the left, shift to the right!
Pop up, push down, byte, byte, byte!

So he leans over the basket and yells out, "Helllloooooo! Where are we?" (They hear the echo several times.)

15 minutes later, they hear this echoing voice: "Helllloooooo! You're lost!!"

One of the men says, "That must have been a mathematician."

Puzzled, one of the other men asks, "Why do you say that?"

The reply: "For three reasons. (1) he took a long time to answer, (2) he was absolutely correct, and (3) his answer was absolutely useless."

Proof (by induction):

Case n=1: In a set with only one horse, it is obvious that all horses in that set are the same color.
Case n=k: Suppose you have a set of k+1 horses. Pull one of these horses out of the set, so that you have k horses. Suppose that all of these horses are the same color. Now put back the horse that you took out, and pull out a different one. Suppose that all of the k horses now in the set are the same color. Then the set of k+1 horses are all the same color. We have k true => k+1 true; therefore all horses are the same color.

Theorem: All horses have an infinite number of legs.

Proof (by intimidation):

Everyone would agree that all horses have an even number of legs. It is also well-known that horses have forelegs in front and two legs in back. 4 + 2 = 6 legs, which is certainly an odd number of legs for a horse to have! Now the only number that is both even and odd is infinity; therefore all horses have an infinite number of legs.
However, suppose that there is a horse somewhere that does not have an infinite number of legs. Well, that would be a horse of a different color; and by the Lemma, it doesn't exist.

Theorem: a cat has nine tails.

Proof:

No cat has eight tails. A cat has one tail more than no cat. Therefore, a cat has nine tails.

                 /\         /\         /\
                /  \       /  \       /  \
                /  \       /  \       /  \
               /    \     /    \     /    \
               /    \     /    \     /    \
              /______\   /______\   /______\
                 ||         ||         ||
                 ||         ||         ||

• I accidentally divided by zero and my paper burst into flames.
• Isaac Newton's birthday.
• I could only get arbitrarily close to my textbook. I couldn't actually reach it.
• I have the proof, but there isn't room to write it in this margin.
• I was watching the World Series and got tied up trying to prove that it converged.
• I have a solar powered calculator and it was cloudy.
• I locked the paper in my trunk but a four-dimensional dog got in and ate it.
• I couldn't figure out whether i am the square of negative one or i is the square root of negative one.
• I took time out to snack on a doughnut and a cup of coffee.
• I spent the rest of the night trying to figure which one to dunk.
• I could have sworn I put the homework inside a Klein bottle, but this morning I couldn't find it.

``Who would like to do the first problem, addition?''

No one raised their hand. She called on Tommy, and with some help he finally got it right.

``Who would like to do the second problem, subtraction?''

Students hid their faces. She called on Mark, who got the problem but there was some suspicion his girlfriend Lisa whispered it to him.

``Who would like to do the third problem, division?''

Now a low collective groan could be heard as everyone looked at nothing in particular. The teacher called on Suzy, who got it right (she has been known to hold back sometimes in front of her friends).

``Who would like to do the last problem, multiplication?''

Tim's hand shot up, surprising everyone in the room. Mrs. Johnson finally gained her composure in the stunned silence. ``Why the enthusiasm, Tim?''

``God said to go fourth and multiply!''

The following is a guide to the weary student of mathematics who is often confronted with terms which are commonly used but rarely defined. In the search for proper definitions for these terms we found no authoritative, nor even recognized, source. Thus, we followed the advice of mathematicians handed down from time immortal: "Wing It."

CLEARLY:

I don't want to write down all the "in- between" steps.

TRIVIAL:

If I have to show you how to do this, you're in the wrong class.

OBVIOUSLY:

I hope you weren't sleeping when we discussed this earlier, because I refuse to repeat it.

RECALL:

I shouldn't have to tell you this, but for those of you who erase your memory tapes after every test...

WLOG (Without Loss Of Generality):

I'm not about to do all the possible cases, so I'll do one and let you figure out the rest.

IT CAN EASILY BE SHOWN:

Even you, in your finite wisdom, should be able to prove this without me holding your hand.

CHECK or CHECK FOR YOURSELF:

This is the boring part of the proof, so you can do it on your own time.

SKETCH OF A PROOF:

I couldn't verify all the details, so I'll break it down into the parts I couldn't prove.

HINT:

The hardest of several possible ways to do a proof.

BRUTE FORCE (AND IGNORANCE):

Four special cases, three counting arguments, two long inductions, "and a partridge in a pair tree."

SOFT PROOF:

One third less filling (of the page) than your regular proof, but it requires two extra years of course work just to understand the terms.

ELEGANT PROOF:

Requires no previous knowledge of the subject matter and is less than ten lines long.

SIMILARLY:

At least one line of the proof of this case is the same as before.

CANONICAL FORM:

4 out of 5 mathematicians surveyed recommended this as the final form for their students who choose to finish.

TFAE (The Following Are Equivalent):

If I say this it means that, and if I say that it means the other thing, and if I say the other thing...

BY A PREVIOUS THEOREM:

I don't remember how it goes (come to think of it I'm not really sure we did this at all), but if I stated it right (or at all), then the rest of this follows.

TWO LINE PROOF:

I'll leave out everything but the conclusion, you can't question 'em if you can't see 'em.

BRIEFLY:

I'm running out of time, so I'll just write and talk faster.

LET'S TALK THROUGH IT:

I don't want to write it on the board lest I make a mistake.

PROCEED FORMALLY:

Manipulate symbols by the rules without any hint of their true meaning (popular in pure math courses).

QUANTIFY:

I can't find anything wrong with your proof except that it won't work if x is a moon of Jupiter (Popular in applied math courses).

PROOF OMITTED:

Trust me, It's true.

Two trains 200 miles apart are moving toward each other; each one is going at a speed of 50 miles per hour. A fly starting on the front of one of them flies back and forth between them at a rate of 75 miles per hour. It does this until the trains collide and crush the fly to death. What is the total distance the fly has flown?

The fly actually hits each train an infinite number of times before it gets crushed, and one could solve the problem the hard way with pencil and paper by summing an infinite series of distances. The easy way is as follows: Since the trains are 200 miles apart and each train is going 50 miles an hour, it takes 2 hours for the trains to collide. Therefore the fly was flying for two hours. Since the fly was flying at a rate of 75 miles per hour, the fly must have flown 150 miles. That's all there is to it.

When this problem was posed to John von Neumann, he immediately replied, "150 miles."

"It is very strange," said the poser, "but nearly everyone tries to sum the infinite series."

"What do you mean, strange?" asked Von Neumann. "That's how I did it!"

Enrico Fermi, while studying in college, was bored by his math classes. He walked up to the professor and said, "My classes are too easy!" The professor looked at him, and said, "Well, I'm sure you'll find this interesting." Then the professor copied 9 problems from a book to a paper and gave the paper to Fermi. A month later, the professor ran into Fermi, "So how are you doing with the problems I gave you?" "Oh, they are very hard. I only managed to solve 6 of them." The professor was visibly shocked, "What!? But those are unsolved problems!"