How someone doesn't understand that they have charged someone an extra 10 bucks for "tax" is beyond me (that seems to be more of a common sense issue than math!) I will say this to everyone....while in high school I was taken off registers at the restaurants I worked at because I have a history of transposing numbers ($1.07 in change becomes $7.01). I have great difficulty reciting long sequences of numbers, especially if they're mixed up with letters, and even while concentrating hard in order to write the '6' out of '601' I will often begin to write '1'. Entering phone numbers usually takes two or three tries until success. While I have taken advanced mathematics, I always have to take longer than the rest of the class and need to double check absolutely every little number and sign. It's very tedious, but I eventually get it done. I didn't have this extra time on a register where customers, of course, want to be dealt with immediately. It was always embarrassing to screw up someone's change, especially on something very simple and appear to be a “Madison”. I feel like I got the short end of the stick as I come from a family of math whizzes!