Scientists and engineers on a train
A group of engineers and computer scientists from the same university are attending a conference in the next town. The decide to take the train. The engineers buy one ticket each. The computer scientists scratch their heads, pool their cash and buy a single ticket. The engineers think this is strange but watching computer scientists get in trouble should be fun. The conductor comes around to get the tickets and all the computer scientists disappear into the bathroom. The conductor knocks on the bathroom door and says "ticket please". They slide the ticket under the door, pool their savings, have a few drinks and arrive at the conference in good form.
On the way home, the engineers buy a single ticket. The computer scientists pool their money and buy n-1 tickets. The engineers scratch their heads, but decide not to worry about it and head to the bar. The conductor comes around and the engineers pile into the bathroom. The computer scientist without a ticket promptly walks over to the bathroom, knocks on the door and says "ticket please."
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