This might seem dumb,but: How do i improve in math?

You don't. Trust me I know. I've been trying since middle school and I still can't get over a D on tests.

We're allowed to use calculators at my school :c and I am in normal math. If I wasn't allowed to use a calculator I would probably be screwed. I really wish I could help you but I honestly don't know what to say. Practice maybe?

Constantly ask ur teacher 4 help even if they don't want 2 give it! That is wat I have done 4 the last few years now!

You and the other students could sign a petition and/or complain to administrators I guess. If the whole class didn't finish, or the majority, that's not fair, especially if you were an A B student, because apparently you know it.

I think you need to complain about your teacher to someone at your school. She sounds extremely unfair and probably needs a talking-to.
The way to improve maths is to revise.

Alternate Testing! If you can't finish a test in time tell your guidance counselor and they might put you in the Alternate Testing room when you write tests and stuff and they will give you extra time especially if not being able to finish cause you a lot of stress. That is what most schools around here are like anyway.

If the class can't finish the entire test, then she is being completely unfair. Math tests should ONLY be given a number of problems that the average time it takes for the class to finish plus a few mais minutes, that way there's no excuse for not finishing the test in time. She needs to get rid of some of the problems on the test to fit the necessary time or allow calculators. It seems like she's a horrible teacher. Its hard to improve times in math unless you're a g-ness or something, but even then math follows rules and steps that you can't always skip. The only way you can improve in math is like other classes, study and do problems over and over again until you got the pattern down.

You said yourself, "The only reason I failed is because we weren't given enough time". So it might not be that you need to improve, but to have mais time on the tests. 45 minutos sounds very short on time for a test so if your teacher won't do anything tell the principle/headteacher (or whatever you call it where you are).
I had an exam a week atrás and it was 2 hours even though we all usually finish within the first hour. The point is 45 minutos is way too short for a test in my opinion...