Current approaches to teaching math emphasize understanding of concepts but perhaps at the expense of fluency. It's cool if a 6 year old can explain that addition and multiplication are the same by drawing a picture -- but if they can't ACTUALLY MULTIPLY WITHOUT DRAWING A PICTURE at age 16, it's gonna be a problem for everyone. A female engineering professor who didn't even take high school algebra until age 26 explains that memorization and repetition are the keys.