A group of engineers and salesmen are traveling via train to a conference. Each of the salesmen buys a ticket, but the engineers buy only one ticket for all of them. One of the sales engineer asks, "How can you all travel on only one ticket?"
"Observe and learn," replies one of the engineers.
Once on the train, the engineers all cram into the lavatory. When the conductor moves down the car collecting tickets, he collects the salesmen's tickets and then knocks on the lavatory door, and says, "ticket please." The door opens a crack, a hand extends and the ticket is handed to the conductor, who then moves on to the next car. The salesmen are amazed.
On the return trip, the salesmen buy one ticket, and the engineers buy none at all. Again the salesmen ask, "How can you travel with no ticket?"
"Observe and learn," replied an engineer. On the train, the salesmen crowd into the lavatory. One of the engineers knocks on the lavatory door and says, "ticket, please."