I was travelling back from Paris today, so I checked out of the hotel and headed towards the nearest Metro station to buy a ticket to CDG, actually I was contemplating only getting a ticket as far as Gard du Nord, dropping my bags there and doing a little sight seeing/shopping, when a local (we’ll, I assume he was local..) saw me stuck at the automatic ticket machine. He asked if I was going to the airport and showed me that I could buy a ticket that took me the whole way to CDG, I already knew this, but didn’t fancy trying to explain that I only wanted to go as far as Gard du Nord at this point, so I gratiously accepted his advice and proceeded to try and buy my ticket.