Dumb question that I can't quite get the answer for....
My Metro pass will have expired by the day we are returning to the airport. I will be at the Montmarte area of Paris, near the Blanche Metro station. The RER leaves from the Gare du Nord a few Metro stops away, or a half hour walk. I know the Metro routes to get to the RER station. One is Blanche exiting at LaChapelle, then walking to the Gare du Nord. A second is Blanche->Barbes, change lines and ride to the Gare du Nord. Once at Gare du Nord take the RER to the airport.
My question is - do I buy the ticket just for the Metro to go to Gare du Nord, then buy the RER ticket there? Or, can I buy the one ticket for the entire trip when I go into the Blanche Metro station? Every website I research is not as clear as I would like, but I think the answer is Yes I can, but I have to use the ticket within a certain time frame before exiting at the Airport turnstile with the ticket??
I would like to just buy one ticket to speed things up, since I am trying to make a non refundable flight to Geneva. If time is an issue, I will spend the 50 Eurors for the cab, but if I have time, I would prefer the train.