Just the tip

Tipping is easy. A twenty percent tip is just a ten percent tip doubled. A ten percent tip is just a matter of moving a decimal. It's simple enough that I've been doing the math in my head for years. The other day I discovered that I'd calculated a twenty percent tip so many times that I was skipping the moving a decimal point to get ten percent bit and going straight to twenty percent. The problem is that I wasn't skipping the doubling part--I was going straight to the twenty percent and then doubling it for a whopping forty percent tip. I'm all for generosity, and I value waitstaff, but my bank account has its limits.

That evening I stared at my receipt puzzled as to why the total was so large. I didn't understand my error for a moment or two. When I figured out where I went wrong, I laughed to myself and scratched out my absurdly generous total. I think it was just the one time that I made the mistake. I caught my error then, no harm done. 

The thing that worries me, though, is that I receive exceptionally good service around town.