I don't know how science majors do this, unless you took calculus in high school and have it count toward college
i double majored in chem and math (i do well with numbers) and finished in 3 with really only 2 extra summer courses. its not bad because it overlaps with a lot of things (i was pre-med also, but thats irrelevant because its fully covered by the chem major).
i did take calc ap courses in high school, started my first fall semester of college with calc 3. all i had to take in addition was linear algebra, differential eq and something else. i took some comp sim/programing class that overlapped with the main university requirements and i think both of my p chem classes somehow counted towards math credits, it was a silly ass loophole that i think i figured out one day when i had to choose the cheapest undergraduate option.
in hindsight, all that was a mistake. college is a time to just take a lot of random classes and be in an academic environment having insignificant conversations, kinda like a less retarded higher learning thread, but with much better looking women