# How do you use math as an adult? **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [January 18, 2020, 2:06pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618 "2020-01-18T14:06:42Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![CelticKnot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/celticknot/32/3392_2.png) [@CelticKnot](https://boards.straightdope.com/u/CelticKnot)\ **Post date:** [January 19, 2020, 10:25pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/41 "2020-01-19T22:25:37Z")
> [@Kropotkin](#): > > Can you ask the students to come up with “real world examples” from their world experience? I have no idea what that might be: calculating interest on cell phone bills? Divvying up snacks that you bring to class? Calculating the volume of farts? > > I’m sure the textbooks have improved but the examples I remember were so esoteric as to be completely confusing. “A farmer wants to divide their acreage between their children equally” just started me thinking, “what is an acreage? Is an acre bigger than our house? Does equal mean equal in size? What if one section is filled with rocks…is that equal? Why can’t the farmer just pace off sections? And why can’t they just agree to work together anyway? Whattya mean, time’s up?” > > Putting them in small groups to devise questions might help, especially with the quiet students who are not inclined to jump up and shout out answers, and you can have them try to work out the solutions and then supply formulas to expand the principle. > > I think, and IANANumberPerson, that one problem with classroom teaching can be some people just “get” the solutions without knowing how they got there and the temptation is to simply seek and reward the right answer. I distinctly remember an 8th grade math class on probability where the answer to the question just jumped out at me and I got it. When the teacher said, “Good! Now use that same reasoning to get the answer to this question,” I had no idea and so went from class superstar to idiot in seconds. > > My wife can easily divide a pie into more or less equal pieces of any number (well, I tell her there’s no point in anything more than eighths, unless the pie is the size of a kitchen table) just by eyeballing it; I am completely mystified by this. If pressed, I deal with the situation of divvying up pie for seven by cutting it into halves, then quarters, then eighths, and eating the extra piece before serving to guests. > > But I suspect your students could come up with questions they would like to solve and that might be exciting for you and them. They’re second graders. They don’t have real world experiences. Most of them are struggling with regrouping, and some don’t even know one-to-one correspondence yet. As for the tutoring, I have to teach what the company provides or help them with their homework. I don’t write lesson plans. So, for sine and the quadratic equation, no, they’re not needed in adult life. ---
**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\ **Post date:** [January 19, 2020, 10:51pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/42 "2020-01-19T22:51:40Z")
In my 10+ years of adulthood I’ve never had to use math beyond basic arithmetic. The most math I’ve ever had to do was calculating my 401k growth and benefits year by year from here on out to my future old age and death, and that didn’t need anything other than an Excel spreadsheet. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [January 19, 2020, 11:05pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/43 "2020-01-19T23:05:08Z")
> [@Derleth](#): > > What is the essence of math? Not numbers: The Pythagorean Theorem was [proven without numbers](https://en.wikipedia.org/wiki/Pythagorean_theorem) multiple times over. Not geometry, as multiple kinds of math have no connection to geometry. Not notation, which is probably more recent than you imagine. > > The essence is logical thinking, taking problems and breaking them down and solving them, with one step leading logically to the next. That kind of logical thinking is the true essence of mathematics, and I use it all the time to develop, test, and debug software. Most programmers don’t have much use for the specific kinds of math that is taught as math in high school and college, and arithmetic is best done by machine anyway, but logical problem-solving is the foundation of the field. OK, but no less than Gauss proclaimed that mathematics is the Queen of the sciences, and number theory is the Queen of mathematics. So let’s not disparage numbers too much. (See also: [numeracy](https://en.wikipedia.org/wiki/Numeracy)) ---
**Author:** ![kopek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kopek/32/337_2.png) [@kopek](https://boards.straightdope.com/u/kopek)\ **Post date:** [January 19, 2020, 11:52pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/44 "2020-01-19T23:52:25Z")
Basic math and percentages I use a lot. More advanced stuff like trig not so much although I do try to keep a working knowledge of basic problem solving. ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [January 20, 2020, 12:01am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/45 "2020-01-20T00:01:43Z")
I use math much more than I use my knowledge of English literature, but I’m glad I learned both. I think it is important to emphasize that math is much more than arithmetic. I pretty much hate arithmetic and thought it was incredibly boring when I learned it in grade school. But I love math. There is no doubt that arithmetic is useful, but kids should be exposed to the beauty of math and the fun of thinking about things in a rigorous and logical way. It is also essential for a wide variety of careers (unlike English literature) including almost all science, engineering , finance, or accounting careers. I cite three examples of the dangers of innumeracy, taken from my own life. - A roommate in college believed that if he was having bad luck at poker, he should start betting big because the odds were now in his favor. Needless to say, we loved to play poker with him. - A neighbor was knitting a baby blanket and wanted to make it twice as long and twice as wide. She bought twice as much yarn and could not understand why she ran out of yarn halfway through. - Another neighbor had a system for choosing lottery numbers. My wife suggested he just use all zeros. He ridiculed this saying, that number would never come up. (I’ve always viewed lotteries as a tax on the innumerate). ---
**Author:** ![JohnGalt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johngalt/32/184_2.png) [@JohnGalt](https://boards.straightdope.com/u/JohnGalt)\ **Post date:** [January 20, 2020, 1:37am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/46 "2020-01-20T01:37:32Z")
My wife wanted to recover an outdoor chair that had rotted its wooden seat. The seat frame was a rhombus made of wood. The wood was so rotten that I couldn’t just copy it, so I measured the two pieces of wood that survived and drew out the shape. I realized that if I divided the two lengths, the arc-tangent of the quotient would be the length of the missing piece. It turned out perfect. If you do any woodworking or trim work, math is really useful. Setting up a miter saw for crown molding uses some weird angles. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [January 20, 2020, 2:10am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/47 "2020-01-20T02:10:09Z")
> [@DPRK](#): > > OK, but no less than Gauss proclaimed that mathematics is the Queen of the sciences, and number theory is the Queen of mathematics. So let’s not disparage numbers too much. (See also: [numeracy](https://en.wikipedia.org/wiki/Numeracy)) It’s still founded on logical thought, and the idea of “number” has been expanded even since Gauss’ time. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [January 20, 2020, 2:25am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/48 "2020-01-20T02:25:00Z")
Knowing that the population of this Board consists of literate and numerate people, I’ll take it as a given that everyone here knows of the book [**Innumeracy: Mathematical Illiteracy and Its Consequences** by John Allen Paulos](https://www.goodreads.com/book/show/186749.Innumeracy). But just in case not, I’ll mention it here. This book as a MUST-READ for anyone interested in the topic of this thread, and especially for teachers. OP, do you know this book? ETA: He begins with this thought-problem that he likes to give students: Estimate how fast your hair grows, _in miles per hour_. The point being, he finds that a lot of students have no concept that hair growth can even be measured in miles per hour. ---
**Author:** ![Baker](https://avatars.discourse-cdn.com/v4/letter/b/bb73d2/32.png) [@Baker](https://boards.straightdope.com/u/Baker)\ **Post date:** [January 20, 2020, 2:34am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/49 "2020-01-20T02:34:10Z")
> [@purplehorseshoe](#): > > Almost three dozen posts, and no references yet about converting grams to quarter ounces? > > I’m not sure if I’m proud or ashamed. I mentioned that in post 31. ---
**Author:** ![nelliebly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nelliebly/32/5422_2.png) [@nelliebly](https://boards.straightdope.com/u/nelliebly)\ **Post date:** [January 20, 2020, 4:37am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/50 "2020-01-20T04:37:37Z")
I use addition, subtraction, multiplication, division, fractions, and percentages every day. But that’s direct use. I may not remember everything I learned in algebra, but as has been mentioned, its value lies in teaching us logic. Once I was teaching an English class the value of certain rules of logic in debate. A kid raised his hand and said, “Excuse me. Why are we studying algebra in an English class?” A golden moment. 🙂 PS Why is it that every freakin’ time I see this thread title, I read it as “How do you use _meth_ as an adult?” ---
**Author:** ![K2500](https://avatars.discourse-cdn.com/v4/letter/k/f6c823/32.png) [@K2500](https://boards.straightdope.com/u/K2500)\ **Post date:** [January 20, 2020, 5:10am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/51 "2020-01-20T05:10:39Z")
> [@nelliebly](#): > > PS Why is it that every freakin’ time I see this thread title, I read it as “How do you use _meth_ as an adult?” Lack of sleep? As an electrician I find my self using some trig formulas and long forms of the basics on a daily basis. ---
**Author:** ![JohnT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnt/32/15048_2.png) [@JohnT](https://boards.straightdope.com/u/JohnT)\ **Post date:** [January 20, 2020, 11:20pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/52 "2020-01-20T23:20:03Z")
I remember _detesting_ having to learn matrix math, just hated it. Wondered when I will ever, ever put calculations in f-in tables, and why I was being taught something I would never, ever use. Now? Now I use it all the time in creating spreadsheets. Go figure. ---
**Author:** ![peccavi](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peccavi/32/388_2.png) [@peccavi](https://boards.straightdope.com/u/peccavi)\ **Post date:** [January 21, 2020, 12:43am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/53 "2020-01-21T00:43:26Z")
> [@Yllaria](#): > > …Most engineering math becomes tables or templates for anything that’s done often. It’s a waste of time to recalculate from principles every time. Your kids might like playing with one of the online asphalt calculators. [Here’s one.](https://pikeindustries.com/products/hot-mix-asphalt) There are more than a few. Some also calculate other matherials. You type in how long the street you’re fixing is (in feet), how wide it is (in feet), and how deep the asphalt is (in inches - hint: you need at least 8 inches for a public street) and it tells you how many tons of asphalt you need to order… This is a trap that engineers fall into. If you don’t have an understanding of the math behind the tables, you risk ending ups with a slipped decimal place, a slightly off conversion, or a just plain wrong answer that you have no way of applying a simple “sanity check” to. Based on my degrees, I’m an engineer and a physicist. One thing from physics I brought to engineering is to always have some expectation (or bounds) of the answer you should get. If the table, calculator, simulator, etc. produces an answer that is significantly off, you need to do some double checking. I’ve seen many a bombed design review when someone in the back of the room (sometimes me) does a back of the envelope calculation and asks why the numbers being presented are so far off from what a rough approximation would expect. ---
**Author:** ![begbert2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/begbert2/32/3357_2.png) [@begbert2](https://boards.straightdope.com/u/begbert2)\ **Post date:** [January 21, 2020, 12:52am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/54 "2020-01-21T00:52:31Z")
If calculator-type math counts, I use it when doing my budget. And I’ve used a little trigonometry to calculate angles for rods in a Lego build I’m designing. But where math _really_ stepped up was in the early and mid-college math classes that focused on theory and, essentially, logical thinking. Set theory, formal proofs, symbolic logic, that sort of thing. I use that stuff here and there without half realizing I’m doing it. It’s made me a better thinker. ---
**Author:** ![phxjcc](https://avatars.discourse-cdn.com/v4/letter/p/8491ac/32.png) [@phxjcc](https://boards.straightdope.com/u/phxjcc)\ **Post date:** [January 21, 2020, 8:01am UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/55 "2020-01-21T08:01:30Z")
Here is one I do all the time… COMMERCIAL: “lease the new WHIZBANGMOBILE for only $500/month for 36 months with $4000 due at signing.” Ok, so—to RENT this car it is going to cost me $22,000, plus taxes, registration and insurance. And why is this a good idea? Every day, get up, take $20 out of your wallet, and flush it down the toilet. Now…you have a “teaching moment” for your students. Or, you can buy a used Camy, Accord, etc and drive it for 10 years. Same money, your choice. ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [January 21, 2020, 12:56pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/56 "2020-01-21T12:56:27Z")
It’s STEM, but I use math all the time: simple multiplication, to get risk levels and prioritize risk management. algebra and arithmetic, to figure out which processes involve less total work. more arithmetic (including %s and fractions), for my invoices. logic (yes it’s actually a branch of maths), to define in detail what programs have to do and not do (the not-do can be very important!). ---
**Author:** ![DorkVader](https://avatars.discourse-cdn.com/v4/letter/d/73ab20/32.png) [@DorkVader](https://boards.straightdope.com/u/DorkVader)\ **Post date:** [January 21, 2020, 1:24pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/57 "2020-01-21T13:24:25Z")
Lets see, when loading household goods on a truck, I play 3D tetris with cubes, cubic rectangles, cylinders, spheres, cones, and what would probably be toruses (and sometimes actual toruses). When setting up an office move, there is an actual formula for figuring out; number of people and where to put them, for figuring out how much time the move will (should) take, and if it is not an enternal move, ie your office is moving to a different building, I have formulas for figuring out how much floor space on the truck each peice of your office stuff, where and how to place it in the load, how many trucks and drivers are optimal etc. Mathematics are totally used in my job. All of it can be taught, in fact the office stuff I learned in a class. The household stuff seems to be generally learned through experience. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [January 21, 2020, 1:44pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/58 "2020-01-21T13:44:22Z")
> [@peccavi](#): > > This is a trap that engineers fall into. If you don’t have an understanding of the math behind the tables, you risk ending ups with a slipped decimal place, a slightly off conversion, or a just plain wrong answer that you have no way of applying a simple “sanity check” to. > > Based on my degrees, I’m an engineer and a physicist. One thing from physics I brought to engineering is to always have some expectation (or bounds) of the answer you should get. If the table, calculator, simulator, etc. produces an answer that is significantly off, you need to do some double checking. I’ve seen many a bombed design review when someone in the back of the room (sometimes me) does a back of the envelope calculation and asks why the numbers being presented are so far off from what a rough approximation would expect. Completely true. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [January 21, 2020, 2:39pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/59 "2020-01-21T14:39:46Z")
My employer"s insurance vendors send me formulas for employer and employee payroll contributions. I have to code it into our payroll software.Life insurance for example has a age / salary table that I update the cost per K of coverage. Other insurance like optional disability is a formula that I update. There’s also a ceiling that caps how much coverage can be purchased. That only effects the high salary employees. Then I have to spot check several employees by hand calculating the withholding and comparing with our Trial payroll reports. The accuracy of the payroll withholding is one of my responsibilities. It’s got to be accurate before payroll is actually run. ---
**Author:** ![zimaane](https://avatars.discourse-cdn.com/v4/letter/z/a3d4f5/32.png) [@zimaane](https://boards.straightdope.com/u/zimaane)\ **Post date:** [January 21, 2020, 3:39pm UTC](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618/60 "2020-01-21T15:39:55Z")
For recipes, I am often adding or dividing fractions - something calls for 2 cups of flour and 1 1/2 cups of water, but I want to use 3 cups of flour, so I have to multiply 1 1/2 by 1 1/2. Then there is financial stuff, like checking how much of a payment goes to interest and how much goes to principal. I once caught a mistake by a department store credit card on that sort of thing. Finally, for fun. I enjoy Numberphile videos and math puzzles like the type Martin Gardner used to publish. I have also dabbled in fractal art, which I create in Excel using simple macros. [Previous page](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618.md?page=2) [Next page](https://boards.straightdope.com/t/how-do-you-use-math-as-an-adult/846618.md?page=4)