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.
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.
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)
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.
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.
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.
It’s still founded on logical thought, and the idea of “number” has been expanded even since Gauss’ time.
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.
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.
I mentioned that in post 31.
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?”
Lack of sleep?
As an electrician I find my self using some trig formulas and long forms of the basics on a daily basis.
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.
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.
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.
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.
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!).
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.
Completely true.
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.
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.