I approach a girl, ask what her number is. Shit tests ensue like "what do you use a number for?" to which I reply "to answer my math homework." Eye contact and smirking she starts telling me her number. So after getting what I came for I say something like "I'll text you" and walk away but in my gut I feel like it was a bad choice and abrupt.

Is there a better way to end approaches? How do your approaches usually go?