Yeah, I was probably too black-and-white sounding about the ability to improve your reasoning through taking courses in my previous post. I have definitely improved at solving problems and understanding proofs since becoming a math major.

For example, the only class I didn't get an A in, differential geometry, I took as a sophomore, and I struggled and spent a lot of time (6-10 hours/week) on homework. But this semester I graded homework for the same class taught by the same teacher, and I find the homework pretty trivial.

I guess I am mostly pessimistic about classes being able to improve your reasoning skills because I very rarely notice classmates who do poorly initially (maybe getting Cs or low Bs) but then start getting mostly As within a few semesters. But maybe this is because most people just don't put in enough effort in their classes. I don't really have many obligations outside of school, so whenever I needed to put in several hours to get every one of the homework problems it didn't bother me at all. I think that probably if you actually enjoy the material and are willing to put in the effort that studying math will improve your logical reasoning skills.

I am doing a PhD in theoretical physics, but essentially math (most of my coauthors are mathematicians) and I disagree with this. The things you do to get a PhD are so specific and more technically difficult than anything you would see in the business world that I don't think it will really help you at all. I would say that once you get into upper undergrad and beyond math is essentially useless except for doing more math or convincing people you are smart and hard working. I know a few mathematicians that work for hedge funds doing more technical stuff than 99% of people in the business world and even for them their PhD work is useless for what they are doing now. Of course they never would have gotten the job without a PhD but that is a different issue.

There's two potential reasons for this:
1) Many students don't care that much about getting A's, so they probably don't work very hard, which causes them to get Cs their entire college career.
2) Maybe everybody's reasoning skills are improving at similar rates, so people remain the same on the relative scale (and since grades are pretty relative, people's course grades are fairly constant).

There is another pretty obvious reason: Some people will never be smart enough to fully comprehend and apply the content.

Also, grades in college are just ranking a student amongst his class mates. Average to below average students probably improve more in general problem solving skills than the best students, but the best students are still better the entire time.

Getting A's compared to C's doesnt mean a "better" reasoning ability, just means they studied more. (Im talking about a person who previously got C's and suddenly got A's)

I think a person who started off as a C(with average work), and put alot of hours in and gets an A doesnt mean he actually got smarter, he just learned his ass off to understand certain concepts. Ask him something outside of the learning material..and he'll be back to being a C student.

Ontopic:
Very interesting topic, I'm european and wondering;
Our education system has 3 years, 1st and 2nd year you do Statistics/Finance/Accounting/Math/Logistics/Management
3th year you specialise in one of those subjects.

If you major Finance in the USA does that mean you ONLY get finance? Or is the system similar to ours, that the main subject is Finance but you do get statistics etc with it?

I like the idea of double majoring computer science, thanks guys.

Okay, I have kind of an unique background in terms of answering OP's question.

I had full scholarship with stipend going to a state university on the east coast so I intentionally avoided graduating.

By the time I graduated, I had 250 credits with declared majors in finance and ECON and a declared minor in Japanese. I was done with math and physics minors curriculum and could have easily finished those majors with 10 or 20 more credits.

I also completed comp sci major but my school did not allow triple majoring.

I interviewed for just about every finance job I could find the listing for, even jobs in operations that I had no intention of taking. Nobody asked me **** from math and physics except an operations management research course but just about everyone was interested in Computer Science. I actually got referred to get an interview with the fixed income trading systems department at a major investment bank when they weren't even recruiting from my school. The job was very attractive with good pay and better hours than IBanking, but I wasn't interested in a programming job.

Physics and math definitely did nuke my GPA a bit as they accounted for the bulk of my Bs that dragged my GPA down to 3.7x (don't remember x) but I was able to list my major GPAs (3.9 for finance/ECON) so that was never a problem for me.

TLDR: in terms of improving job prospects, comp sci is your best bet, at least at the undergrad level.

Damn it haha. I was just beginning to set my mind on math.

For the job you have now, do you use your CS knowledge much, and is it necessary to constantly learn more to keep up with the changing computer environment?

I was somewhat worried about my GPA suffering if I were to do math, but I was hoping I would be able to list my major specific GPAs.

I was thinking that law school would also help one to present,articulate himself better(So a leader role seems more likely to happen). Knowing what a company can and cant do legally also seems nice when you're an accountant?

It hasnt been suggested in this thread though, I assume for a reason, why?

I actually did suggest it law school but then dismissed it because while a law degree is useful the process of going to law school is a waste of time.

Also, while I'm not certain if this is true in the States but you generally need at least two years (often three) of undergrad to get into law school so he'd be looking at a minimum of five years and likely six.

Ah well, law school in europe(holland) is pretty easy to get into.
Our university gives both law and business majors.

Our system is pretty nice, I can do a Law major for FREE anywhere in the country because I already do a business major.

Would my situation change your opinion? Would Law school be a great asset for a business major?

Looking at the requirements for CS Major at my school, the only math classes that are required are: calc 1 and 2 and business stat (which I took and was a complete joke). Is this similar to other CS programs?

We had some exchange students from Europe and I got the impression the law program was something insane like six or seven years.

Not really. I think a law degree is very useful to have but law school is intellectual dead time. OP wants to improve critical thinking and you don't really do that at law school. The cost isn't the issue and doing a joint degree is quite common (my school offered a LLB/MBA joint program) but other than the actual degree the time spent at law school is a waste.

We were required to take two half courses in second year and they were brutal -- I'd say 30-40% of students had to retake them. There was also an applied logic class in second or third year that I believe was mandatory but I can't be certain.

What exactly did you do in law school?