Some young but very ambitious students (yeah, yeah, some of you are reading this post on my blog right now :-)) have been asking me why would they need to know Maths if they want to become economists (in industry or academia) and what Maths courses are most suitable for them and how much Maths would they actually use in practice anyway...
These are very interesting and very pertinent questions and obviously they were asked and answered before. By many, many times. I'll thefore select a few such answers for you, among those that I largely agree with. To start up, I am very lucky to be able to refer all of you to Greg Mankiw's detailed answers to the questions directly relating Maths to your further careers as economists. First, why do aspiring economists need Maths and second, which Maths courses are a minimum that you should plan to take. By the way, for those of you interested in doing a PhD in Economics, I'd take professor Mankiw's advice very seriously: "if you are thinking about a PhD program in economics, you are advised to take math courses until it hurts" :-).
And if you want something to complement the above - and, at the same time, a more general perspective on why a Maths education might be useful - I also recommend you to read Gian-Carlo Rota's "10 lessons of an MIT education" (it's not the MIT part that's important for my purpose here :-)) and I am referring in this case (there are also things among these 10 lessons that I do not fully agree with, but it's not time to voice my discontent with that :-)) particularly to his Lesson number 10, here's the relevant part: "Mathematics is still the queen of the sciences [...] When an undergraduate asks me whether he or she should major in mathematics rather than in another field that I will simply call X, my answer is the following: "If you major in mathematics, you can switch to X anytime you want to, but not the other way around."
For the last part of the questions above, on how much Maths would you actually use in practice beyond absurd requirements of some crazed professors :-): that largely depends on what you will actually do, whether you'll be working as an academic or as a consultant of some sort etc (Greg Mankiw already had a bit on this, at the links mentioned above). But that aside, a good Maths training will give you something potentially more important, whatever you'll be doing: it will enable you to think logically in whatever situations you will face (and that is what I'd call the 'qualitative' bonus of having done Maths), plus it will give you a technical basis and will allow you to rely on your own skills for most day-to-day computing, accounting, investing, issues (and that is what I'd label the 'quantitative' methodology advantage that comes with having learnt Maths): à propos, I recall here a pertinent citation attributed to Anatole France: "People who don't count won't count"... Furthermore, and this is more important than many think, once you did it properly and you understood it (in Maths you do not memorize- if you try that, you don't stand a chance- you need to understand, you need to get used to it...), you will always be able to know how and where to look for particular bits, whenever you need to apply them again (that was contained also within Rota's rules, if you read carefully, in his Lesson 3: By and large, "knowing how" matters more than "knowing what." ).