As Winnie Cooper on the hit sitcom "The Wonder Years," Danica McKellar was the pretty girl who stole young boys' hearts with a combination of sweetness and smarts. But even her most ardent fans had no idea exactly how brainy she was.

McKellar went on to major in mathematics at UCLA and became something of a math genius in the process, earning the rare distinction of co-authoring a professional theorem as an undergraduate. (The theorem is now known as the Chayes-McKellar-Winn Theorem.) While McKellar has since grown up and her acting career prospered with regular roles on series, such as "The West Wing," her passion for math could not be denied.

In order to bring this passion to the public, McKellar recently released "Math Doesn't Suck: How to Survive Middle-School Math Without Losing Your Mind or Breaking a Nail," a book for middle-school girls that walks them through the perilous world of middle-school math while also teaching them that intelligence is nothing to be ashamed of, and that beauty and brains are as solid a combination as Winnie Cooper and Kevin Arnold.

Bankrate spoke to McKellar about her new book, and the great loves of her life -- acting and mathematics.

Bankrate: You mention in the book that you hated math until the 7th grade. What turned it around for you?

Danica McKellar: It wasn't that I always hated it, I just went through a phase in middle school. Middle-school math presents challenges that don't exist in elementary school, where long division is as hard as it gets. At the same time, middle-school kids are dealing with a slew of self-esteem issues. It's a confusing time where you ask for the first time, "Who am I?" So math gets hard at the same time you're asking yourself, "Who am I?" Then it's, "I think I don't really like math."

Bankrate: This was before or after "The Wonder Years?”

Danica McKellar: I started shooting "The Wonder Years" in the 7th grade. This was right before then. We shot the pilot near the beginning of the year in 7th grade, and midway through that grade I had my math revelation.