I took a combination linear algebra/series course in college and barely remembered anything from it. Years later, when I was learning 3D graphics, almost any t

I took a combination linear algebra/series course in college and barely remembered anything from it. Years later, when I was learning 3D graphics, almost any time I did matrix-matrix or matrix-vector multiplication, I had to look up a formula or painfully work through remembering how it worked. My attempts to memorize the simple algorithm all failed. Then I bought Strang's book, watched the OCW lectures, and did the homework. Now any time I have to do or think about a matrix multiplication, Strang's voice echoes in my head, "combinations of columns." There is something special about his words, his tone of voice, and his repetition, which all together make it click for me.