Joke: Why is 6 afraid of 7? Because 7 ate 9! You don’t get this? Perhaps you suffer from dyscalculia — a learning disability that creates severe difficulty in understanding and using functions or symbols needed for success in mathematics. (Or maybe this joke is very stupid!) Like dyslexia, which affects reading ability, dyscalculia can be caused by a visual perceptual deficit. The UK government’s Department for Education and Skills includes this numeracy problem in its leaflet on Guidance to support pupils with dsylexia and dyscalculia. What brought this to my mind was hearing someone at my household this weekend complain that the DVD burning process was only “5/3rds” done! Maybe fractions should be put in a special category — they really are terribly hard to fathom. I thought I had fractions mastered until the time I traveled into the hinterlands of western Wisconsin into a chain of lakes peppered with cabins. The one I wanted was on 178&23/32nd street. It challenged me to calculate that I ought to keep on going past 178&1/2, 178&5/8th and 178&11/16th streets.