Known for portraying Winnie Cooper in the coming-of-age television series "The Wonder Years," actress Danica McKellar has taken on several non-acting roles since then—including mathematician and New York Times best-selling author.

Growing up, the actress says she was always good at math. "I took the AP Calculus BC exam at the end of high school and scored a 5 which the highest score you could get," McKellar told CNBC's "On the Money" in an interview.