Yeah, that's one of the reasons I had a problem with it too and just decided to round up a little to make it slightly faster and show more of a profit than break even. I like your way of doing it as well. Maybe I just tried to over-simplify it for myself to make things quicker, but perhaps over-complicated it in the end.

With .38*50, I'd just round that up to .4 and just make up 20 over the next streets.