I do know. I started college as a Math Major and graduated with a degree in History. You can imagine what happened in the intervening years.
LOL! At least History of Math did double duty.
Most people really have no concept. Engineers, who are often considered among the most intelligent people in the university are weeded out by the Calculus sequence. For everybody else reading this, Abstract Algebra is a whole different animal. Much much harder.
And then there's grad school.