"What, you want a quarter pound?"
"No, four tenths--for a burger."
(looking at me like I'm crazy) "Four tenths?"
"Yeah, it is. Four tenths of a pound."
I think I figured out the right way to ask for 0.4 pounds of ground beef. One asks for "point forty". I'll try it next time.
The burger, of course, was delicious. I make fantastic burgers.