A mathematician, a biologist, and a physicist are sitting in a street cafe watching people going in and coming out of the house on the other side of the street.

First they see two people going into the house. Time passes. After a while they notice three people coming out of the house.

The physicist: "The measurement wasn't accurate."
The biologists: "They have reproduced".
The mathematician: "If exactly one person now enters the house then it will be empty again."

Joke Nodes: Geek Jokes: Real life applications of mathematics

I've always had it in my head that if being a web developer ever stops working out well for me, and if I can afford the pay cut, I'll go get a high school teaching degree and become one of the few mathematics teachers in this country to actually know what he's doing. I've decided my very first day in front of my own class will go something like this:

"Okay, before we do anything in this class I'd like to get a little background information on who I'm dealing with this semester. Would everyone who wants to be in this class please raise your hand?"

(one or two students do so)

"Okay, and now will everybody who's taking this class because it's required for them to graduate please raise their hand?"

(everybody else does so)

"All right, that's about what I thought. Now, of those who just raised their hands, would you raise them again if you're of the conviction that you're never, ever going to use what you learn in here again after you leave school?"

(about ninety percent of the class raise their hands)

"Okay, let's start with you. What do you want to do for a living after you finish school?"

(a brief hesitation) "Um, teaching. Grade school."

"Alright, that's good. Now tell me, if you weigh your students' grades so that their tests are worth twice as much as a homework assignment, and they receive one test a week and five homework assignments a week, and one of your students is averaging 80% on each test and homework assignment with six weeks left in the quarter, will that student be able to reach 90% for the class if they start getting 100% on each homework assignment for the rest of the year?"

"Um..." (long pause, I don't stop looking at the student) "...I have no idea."

(moving on to the next student who had raised their hand) "Now you. What do you want to do for a living after school?"

(trying to be clever) "I'm going to ring registers at Wal-Mart."

"Okay, humble but useful. Tell me, if you ring up a customer's order at $27.87, and they hand you a $50 bill, and after you type it into the register and see $22.13 you're handed an additional two dollars, two pennies and a dime, what's the best change you can give him back?"

"Oh, come on, people don't do stuff like that."

"Really? I do, all the time." (moving on) "What do you want to do for a living?"

"Auto mechanic."

"Great, we need guys like you! Tell me, my car is supposed to get 28 miles per gallon according to the sticker when I bought it. I just drove 325 miles to get to your station, and about twenty miles back I refilled my tank with 12.84 gallons of gas. Do I need to get my engine looked at or not?"

(confidently) "Can I charge you for the inspection?"

"Ah, a true capitalist! You, what do you want to do?"


"Ooh, you poor soul. The office network printer just ran out of paper this morning, and the vice president just let you know that she needs eighteen copies of a 87-page double-sided presentation for an eleven o'clock meeting, plus binders. If binders cost $4.99 apiece at Office Max and printer paper costs $8.99 per hundred sheets, and sales tax is 7.5 percent, how many packages of paper do you need to buy and can you do it with the $100 bill you just found in the company till?"

"That's accounting's problem."

"Not if your PHB says it isn't. You, what do you want to do?"

"Army. I'm joining the ROTC."

"Good for you! Your drill sergeant just told you to peel all the potatoes in the pantry. You start at noon. After one hour, you estimate that you're about one-sixth of the way done when the cook drops off enough potatoes to increase your "to do" pile by half. How much do you need to increase your output by to be finished by dinner at six?"


"You, what do you want to do?"


"Oboy, you need me right now. Your company's 401(k) matching contribution just dropped from ten percent to eight, and you've got twenty years until retirement. You didn't put your retirement savings into the company's stock, like a good girl, so you won't be hit by the resulting drop in their stock price when the news gets out. Assuming your 401(k) continues to rise at 7.2 percent per year as it has been, on the average, how much do you need to increase your contribution by to retire with the same amount of money you'd originally planned on?"

"I hired a finiancial planner to do that for me."

"His calendar just filled up when every other employee heard the news; you're on your own. You, what do you want to do?"

"I'm going to be an architect."

"Perfect! You've been assigned to build a two-story four-bedroom home on a lot with a lot of shade trees, and you've been told to preserve them. You don't know how tall the tree is, but on a sunny day its lower branches cast a shadow eighteen feet away from the base of the tree. You measure your own shadow and find it to be four feet, ten inches. How far off the ground are the lower branches and are they going to be in the way of your roof?"

"Um... don't know."

(addressing the class) "None of these word problems require more than a little algebra and maybe a dose of geometry. But they're the kinds of things you can be expected to answer on any given day after you join the working world, and a calculator isn't going to be enough to solve them. As long as you remain a member of modern society, you need to be able to know how to push these kinds of numbers around. By the time you're done with this class, you're going to know how."

One day, a six engineers and six mathematicians were heading to a national conference together, and reasoned that taking the train would be the cheapest and most efficient way to go. Being mathemticians, the latter group didn't have much money to spare, so they told the engineers that they could all get on the train with one ticket.

"No way, you'll never get away with it!" Proclaimed one of the engineers. The engineers then bought six tickets, while the mathematicians proceeded to buy one. So they all got onto the train, and when the guy came around to take tickets, all of the mathematicians piled into the bathroom.

"Ticket, please!" said the ticketmaster after knocking on the bathroom door. He was handed one ticket, and walked away.

The mathematicians were pretty proud of themselves for proving tbe engineers wrong, so they had a good time at the conference. Then when they decided to head home, the engineers bought one ticket, because if the mathematicians got away with it why couldnt they? The mathematicians decided to go even farther with their ploy and told the engineers that they were going to get on the train with no tickets at all. The engineers couldnt believe this, no tickets at all! So they all got onto the train, and when the guy came around the engineers all piled in one bathroom and the mathematicians all piled into the one next to them. Then one of the mathematicians stuck one of his hands out of the stall and said: "Ticket, please!"


Note: You can tell I'm a mathematician, right?

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