I faced the opposite decision... a double major in math and CS or just the math major, and decided to do only the math major. It was the best decision of my col

I faced the opposite decision... a double major in math and CS or just the math major, and decided to do only the math major. It was the best decision of my college career. But I still took the upper level CS courses that interested me! So drop the math major, but learn Galois theory (or whatever) anyway. That said, I don't recommend graduating in three unless for economic reasons you have to. If you can, take the fourth -- study abroad is awesome, as others suggested -- it is also a great chance to take advanced courses in other disciplines. I took an upper-level philosophy course, it was hard and I learned a ton.