Preposition: Which one is correct and why

[harpreet1205]

Hi Ron,


1. Which train did you come on?
2. Which train did you come by?

I have come across both the sentences. I am not sure which one is correct. Please tell me which preposition is correct and why?

Regards,
Harpreet

[RonPurewal]

did you see these sentences in any material that's actually related to the GMAT exam? if so, where?

(this seems to be a question about informal usage, and thus irrelevant to this exam.)