### Just For Fun

### Mathematical Jokes

**An engineer thinks that his equations are an approximation to reality.**

**A physicist thinks reality is an approximation to his equations. **

**A mathematician doesn't care.**

**There are three kinds of people in the world; those who can count and those who can't.****The Evolution of Math Teaching**

**1970s: A peasant sells a bag of potatoes for $10. His costs amount to 4/5 of his selling price. What is his profit?**

**1980s: A farmer sells a bag of potatoes for $10. His costs amount to 4/5 of his selling price, that is, $8. What is his profit?**

**1990s : A farmer exchanges a set P of potatoes with set M of money. The cardinality of the set M is equal to 10, and each element of M is worth $1. Draw ten big dots representing the elements of M. The set C of production costs is composed of two big dots less than the set M. Represent C as a subset of M and give the answer to the question: What is the cardinality of the set of profits?**

**2000s: A farmer sells a bag of potatoes for $10. His production costs are $8, and his profit is $2. Underline the word "potatoes" and discuss with your classmates.**

**2010s: A farmer sells a bag of potatoes for $10. His or her production costs are 0.80 of his or her revenue. On your calculator, graph revenue vs. costs. Run the POTATO program to determine the profit. Discuss the result with students in your group. Write a brief essay that analyzes this example in the real world of economics.**

**There are 10 types of people.**

**Those who understand binary and those who don't.**

**Q: How does a math professor propose to his fiancée?**

**A: With a polynomial ring!**

**It takes two general relativists to change a light bulb.**

**One holds the bulb, while the other rotates the universe.**

**There really are only two types of people in the world.**

**Those that DON'T DO MATH, and those that take care of them.**

**A father who is very much concerned about his son's bad grades in math decides to register him at a catholic school.**

**After his first term there, the son brings home his report card: He's getting "A"s in math. **

**The father is, of course, pleased, but wants to know: **

**"Why are your math grades suddenly so good?" **

**"You know", the son explains, "when I walked into the classroom the first day, and I saw that guy on the wall nailed to a plus sign, I knew one thing: This place means business!"**

**Q: What will a logician choose: a half of an egg or eternal bliss in the afterlife?**

**...**

**...**

**A: A half of an egg! **

**Why?**

**Because nothing is better than eternal bliss in the afterlife, and a half of an egg is better than nothing.**

**The highest moments in the life of a mathematician are the first few moments after one has proved the result, but before one finds the mistake.**

### Dictionary of Definitions of Terms Commonly Used in Mathematics Lectures

**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.

**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.

**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 them if you can't see them.

**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.

**QUANTIFY: **I can't find anything wrong with your proof except that it won't work if x is a moon of Jupiter.

**PROOF OMITTED: **Trust me, It's true.