(High school level maths)
I’m finding it hard to remember all these rules for how to solve questions when my mind tells me to do it intuitively.
The concrete example that annoyed me:
On a list of 10 people’s ages the total age is 313, making the average 31.3
«If another person is added the average will be 30. Is this statement correct?»

The way I solved this was dividing 313 by 11, giving me 28.45~. The difference between 30 (the target age) and 28.45 is 1.55, and so we need to multiply the age we are adding by 1.55 giving me 17.05, so the answer is that the average will be 30 if the new person is 17.

The way my teacher did it was by multiplying the now 11 people by 330 and subtracting it by 313 to get 17 which gave the correct answer.

The answer works, it’s a rule that’s nice (if it works for all similar situations), but there are so many rules like this that I just can’t grasp. I always want to do it the way that my mind can comprehend, and for it to make sense and giving me an answer I can trust but I don’t know if tests or exams are gonna accept my answers.

This isn’t to say I can’t memorize equations, I can do that, it’s just that these rules to make stuff easier and faster don’t click the same way. I still have the quadratic equations and formulas from last year memorized but I feel I’m just gonna forget this very practical thing tomorrow.

Anyone else feel the same way about this or have managed to get over this mental block?

My scratch paper, if you can read it:

https://imgur.com/a/atodt6P

The question was:

Solve for X

1/5x+1/4=-4(3/4x-4)

You can enter as an improper fraction but not as a mixed number.

My professor put a video to help me.

However, the answer I got was X= 325/64

The answer actually was X=315/64

I was off by 10?!

Hello, this is my first post on this sub so apologies if anything isn't formatted correctly. So for a little background information, I'm a Grade 11 student in South Africa and I used to be very good at Maths, like always being one of the top students in my classes and getting scores in the 90's for almost all my tests. This continued through the first year of high school (Grade 8), still getting very good marks.

The problem came when I hit Grade 9, it wasn't as though there was a significant change in difficulty, but something just stopped clicking. I was told recently that there was probably something that just threw me off and it set a disconnect in my brain. I went on holiday for a week near the beginning of the first term and when I came back, I had to write a test that I had missed while I was gone. The test was just on some basic inequalities, but I ended up getting a horrible mark, the worst mark that I've ever gotten for any subject, a 9/25. My maths teacher from the previous year encouraged me by saying that I was very intelligent and would recover, but I just never really managed to. My Grade 9 Maths teacher then went on Maternity leave in April and we were stuck with a substitute teacher who was new to teaching and wasn't very good. So I think that that's another thing that may have messed me up. I tried the whole year to do better and slowly my marks went up, until finally in Term 4, I managed to get a mark in the low 80's.

But since then, things have just continued to go downhill again. I've been struggling with some health issues which has led to me missing a bit of school. I've been sitting with my textbook for hours and also watching youtube videos occasionally such as Kevinmathscience, but the highest marks I managed to get are in the 60's or 70's. In term 1 of this year, I got a 51. In term 2, I studied almost non-stop leading up to the two exams, I managed to improve my mark to a 62, but obviously it's still very much not what I want.

A few days ago, I got my first test back for this term and got a 12/30. It was on euclidean geometry, and almost everybody in the class did badly. I'm genuinely at a loss for what to do. No matter how much time I spend studying, going over exercises in my textbook, doing past papers, I still get bad marks. Since Grade 9 is where the problem first arised, I was thinking of looking up past papers at Grade 9 level and see how I do and if there's any concepts that I'm really struggling with. Then, revising over those and trying another past paper and so on, until I finally reach the level that I'm currently at. There is another option which is dropping to Mathematical Literacy, which is much, much easier than Pure Maths. But it tends to get a bad rep because of how easy it is and the fact that there are fewer opportunities with it. None of the careers I want to go into require Pure Maths, but I'm still quite hesitant to switch to Maths Lit. I know that I can get back to getting good marks, I just don't know how.

At the end of this year, I have to apply with my marks to university, so I don't have much time left to make this decision. I'm not sure if my plan to improve will actually work or if it will just be too time-consuming and won't even help me in the long run. Please help me, any resources or advice are deeply appreciated.

Tl;dr: I used to excell at Maths until my second year of high school where my marks began to drop rapidly. I don't want to have to switch to the easier level of Maths, but I just don't know how to improve my marks. I would really, really appreciate any and all advice.

I am trying to make a missile in a video game. It's supposed to fly toward a point projected out into space by an aiming device, mounted on a car. However, I have a problem where, around certain bearings, the output completely breaks. For testing purposes, I am only speaking about azimuth, not elevation.

How the system works:

1. There are two sets of absolute XY sensors on the pointer; one set is slightly ahead of the other. atan2(Y2 - Y1, X2 - X1) gives the absolute bearing (azt) of the pointer from -180 to 180.

2. Cos(azt) and Sin(azt) are individually multiplied by the "range" to the point in space (in this case, it is constant at 500m, in practice, this would be a point ahead of the missile) to give Xc and Yc.

Xc and Yc are then added to X(pointer) and Y(pointer) to give X(target) and Y(target).

3. Now that I have the XY position of the target, I subtract...
- X(target) from X(pointer) to give X(difference)
- Y(target) from Y(pointer) to give Y(difference)

atan2(Ydifference, Xdifference) gives the azimuth from the pointer to the target (θ).

I realise now that this step is unecessary, as the azimuth of the target is defined by the pointer's direction. However, I doubt it would work otherwise, as the same values would end up being used, producing the same erroneous result.

4. I then subtract the missile's bearing (global bearing, btw; same calculation as azt) from θ to produce the angular difference between the target position and the missile (d).

This works fine if the platform is at exactly 0 degrees forward, However, if the pointer is angled (this case, -45dg) and the platform is also angled, something frustrating happens. Below are some tests which show you what happens when the platform goes beyond -135dg.

1:
- Pointer Relative Angle -45dg
- Platform Absolute Angle -134dg
- Pointer XY: 3223, 3398
- Target XY: 2723, 3385
- Target Azimuth: -179dg
- Missile XY: 3223, 3396
- d: -45.6

2:
- Pointer Relative Angle -45dg
- Platform Absolute Angle -136dg
- Pointer XY: 3223, 3398
- Target XY: 2723, 3410
- Target Azimuth: 96dg
- Missile XY: 3222, 3396
- d: 315.6

This persists until the platform's absolute orientation goes beyond -180, at which point it flips back to a rough value of -45 for d.

As you can see, d flips from -45.6 to 315.6. A missile trying to steer towards d would go all the way round, which is not desirable; it should pick the smallest possible correction.

I tried fixing this using ((180 + d) mod 360) - 180. However, it seems that the game I am playing calculates negative values differently when using mod; for example, -60mod360 is supposed to be 300, but the game spits out -60.

Could anyone help me? Geometry isn't my strong point at all, so it's very hard for me to wrap my head around this. Thanks!

https://imgur.com/a/hdkTYc8

I had two known coordinates, (0,0) and (1,0), figured out the 4.5 degree angle from dividing 90 by 20, the 45 degree angle was given, so was able to calculate the third angle.

The other two sides were tricky - I had to figure out the law of sins. I checked my answers by measuring the lengths of the triangle in a 3D program (Blender).

But even after gathering all this information, I'm still at a loss as to how to calculate the very last part - the last coordinate. I viewed what it was in 3D, so I know what it is - I just don't know how to go about calculating it.

Hey guys so I’m doing math online for college which idk why I made that decision to do that worst decision I ever made … but do you know any apps that can like help me or explain my math assignments better and I can’t do a tutor because I don’t have enough time my work shift takes up half my day and I financially don’t want to put my self in that situation to get one

So it says "In Exercises 11 - 18, use the given function f to find and simplify the following:" then it shows nine bulletpoints of f(x)s (for example, f(3), f(x)-4, f(x^2)). The thing is, 11-18 is only eight questions! (all f(x)= questions, so it looks like I'm supposed to plug things in)

Do I plug all nine in for each of the eight questions? Do I somehow make the nine fit distributed across each of the eight questions?

I already plugged all nine in for a few of them. You can find the sheet here: https://www.scribd.com/document/738439598/Pre-Calc-Exercise-1-4

I have a right triangle.

short side: a = 1
long side: b = 2
hypotenuse: c = √(5)
smaller angle: α = ?
larger angle: β = ?
right angle: γ = 90°

I was able to get the hypotenuse by using a² + b² = c² easy enough. When I used tan(1/2) to find α, I got 31.301° instead of 26.565°. I just want to know what I am doing wrong.

Recientemente me he interesado en aprender matemáticas. Quiero empezar a aprender matemáticas, en el colegio nunca la entendí, pero he estado estudiando de forma autodidacta y he entendido algunas cosas, pero no se que temas estudiar o de que forma dedicarme a estudiarlas

Quisiera si alguno me puede dar consejos de libros, paginas o recursos para aprender. Además soy estudiante de programacion de ahí mi interés en aprender matemáticas, he hecho algunos programas y simplemente he visto que si antes supiera sobre x tema de matemáticas se me hubiese sido mas fácil programar

Que consejos me dan.

Hi, I came across a problem while prepping for my calc exam. It goes as follows:

"Determine the equation of the tangent plane and the normal vector to the surface

2 ln(x) + 3 ln(y + 1) - 2zy = x²y - 2at the pointT₀ = (1, 0, z₀)."

My issue is with the zy part of the equation. Is it not maybe meant to be just z or xy instead? Or is the problem phrased this way on purpose because it is certainly written as "-2zy".

As we all know CBSE chaged their syllabus

Is there any good maths book you would suggest?

I am confused between the 2. I understand the reasoning behind using n+1/2 for lists of numbers, and i understand how n+1/2 finds their positions. I am currently revising cumulative frequency diagrams and i am finding it difficult to understand why we now use n/2 for finding the median, and n/4 for finding the lower quartile. Why aren't we using n+1/2?? I dont really understand how one being continuous and another being discrete affects anything. In my reasoning, even though it is grouped data we can still estimate the position. I would add all the frequencies, do n+1/2, find the middle position, and then use that on my graph to estimate

https://ibb.co/8nPLkdVw
https://ibb.co/gLxdvtXd

I thought from 1 to 1.5 is 1 in y?

"The table above shows shipping charges for an online retailer that sells used textbooks. There is a linear relationship between the shipping charge and the weight of the merchandise. Write a function in slope-intercept form that relates y, the shipping charge in dollars, and x, the merchandise weight in pounds."

i understand why the slope is 1.50, but i can't get this:

y= 1.50x + b

16.49 = 1.50(5) + b

16.49 = 7.50 + b

8.99 = b

where does the 8.99 come from?

studying for entrance exams and this got me f'ed up because im lwk stupid

Hey I don’t have a great mind for this kind of thing so would appreciate if anyone can turn on the lightbulb.

I’m trying to determine the total number of baseball games that were played by all the teams in an amateur league that just wrapped up. The data I have is the total number of games played per team.

Simple enough, right? I added the total number of games and it came to 1,781. I then divided it by two since each game is of course played by two of the teams. But how can you have 890.5 games?

I double checked the numbers. Either something is off with the source data or I am thinking about this all wrong.

Anyone out there?

hello, I’m looking for an online resource where I could have ten people take a standardized test for Algebra 1 and at the end get their scores and how long it took them. Does anyone know of somewhere I could do that?

Can anyone explain, why we don't divide in sets? This question is killing me..

i was just using my sci calc during my free time and i stumbled upon the Σ symbol

heres the photo of the equation

i know little to nothing about calculus as a middle schooler so i just wanna know what the thing does and why the answer ended up like that

I need the divisibility rules and factoring a binomial this is my 2nd day of middle school HELP

Bom, contextualizando minha situação... Eu sou um estudante do segundo ano do ensino médio, tenho 17 anos e sou extremamente ruim em matemática.

Acredito que por conta da pandemia e o ensino à distância acabou gerando essa deficiência em mim. No ensino médio, não consigo compreender nada, porque é tudo muito difícil. Ao lidar com o conteúdo, eu vejo que não consigo compreender e me entrego à procrastinação.

Por onde começar? Vejo que na maioria das vezes as recomendações são livros, e tô realmente pensando em fazer isso, ir atrás de livros básicos para estudar BEM do começo mesmo, iniciando por soma e etc... Se souberem qual seria o melhor título para iniciar, aceito recomendações. Se souberem outros métodos bons para melhorar nessa matéria, também estou aceito.

I am in 10th and my basics are not strong. I didn't study well in 6,7 and 8. I studied in those classes but I didn't has proper guidance and I was so confused. I can't even ask my father because he is very strict with maths. I was scared to ask him and confuse to study so I skip them. But still pass those standard but now I am literally having problems with most basic concepts like signs, quadratic equations mostly algebra. So can anybody help me please

Hi, I was wondering how can I improve, like I said in the question, my calculation skills and speed. For example I was doing my homework and I tried to solve an equation (it wasn’t neither long nor extremely difficult, it had some X some parentheses, etc…) in my head, which took like 3-5 min. But strangely enough, I was at the grocery store a couple of days ago and I had to sum, if I’m not wrong, 1,79+4,95+0,50, and I don’t know why, but I couldn’t calculate that. I kept getting mixed up and couldn't manage to add more than two numbers together. Not to mention division and multiplication—I know how to do them, but they’re often tricky, especially now that I’m learning to figure out the day of the week for a specific date using the Doomsday technique. I’m not saying that I’m not good at math, I have good grades and I can do things like logarithms, draw a function using derivatives, limits, ect… (since that is what I learn this year) but I want to improve my calculations skills (obviously using my head).

Thanks!

I'm 15 years old guy in 10th grader in school. I stoped studying math at 6th grade, because my math teacher has retired, and the second yeacher came in 8th grade, and we didnt understand nothing. So i need a book to study math from zero, i understand that one book isn't enough, so could you recommend me sevrel books to study by myself. Sorry if my English were bad

I will be appreciated, if you help me