Comrade Lenin, as President of the Union of Soviet Socialist Republic, has lots of work to do, and his workdays finish late at night. Lenin has been married for decades with a comrade and activist, since the days of clandestinity, and loves her very dearly, they have shared everything and have built together a new world, and President Lenin would never divorce her. She has surely not become arrogant with power, and lives in a modest but dignified apartment. Comrade Lenin is, of course, not bound by the bourgeois morality and the contradictory bourgeois family structure, and he has a very attractive young girlfriend. She, too, is not corrupt with power and lives in a modest but dignified apartment not far away. Comrade Lenin, who is very scrupulous and very upright, has thought at length about the best arrangements, so that he should be fair to both, and they have found his suggestion a perfect solution. When he finishes working – at a random time in the evening – he walks from the Kremlin to the subway station, and boards the first train that arrives. According to the direction of the train, he will spend the night with his wife or his lover, because it happens that the two apartments are located on the same subway line, but one needs to take the train in opposite directions.

However, on average, in a month, he spends a night with his wife and the rest of the time with his attractive girl. How can this be?

Credits and source attribution

I do not know who first suggested this problem, which I heard from my teachers (a number of them) and assumed it was a pretty standard one. If someone does, please let us know. I’ve even heard having been credited with it myself: I am flattered, however, this attribution is incorrect.