I recently paid a $5.65 bill with a $10 bill and 65 cents, to get rid of some change. The poor child was so confused. My dad started life as an accountant, in the '40s. Told me this story. Once a fellow accountant needed to multiply 12 x 12. Used a pencil and paper. Good life lesson. I have always, since that day, known what 12 x 12 was.