I was at the big box lumber store a couple of years ago buying a bundle of 1x3 strapping.  The bundle was 3 pcs wide by 9 pcs high.  The young women kept trying to count them up individually (and getting a different answer each time).  I kept on trying to tell her that there were 27 pieces and I knew this because 3 x 9 = 27.  She looked at me as if I was from Mars.