Gara Nazionale 1986 - 7

[ngshya]

Riporto il testo in inglese per evitare errori di traduzione.

On a long enough highway, a passenger in a bus observes the traffic. He notes that, during an hour, the bass going with a constant velocity overpasses $ $a$ $ cars and gets overpassed by $ $b$ $ cars, while $ $c$ $ cars pass in the opposite direction. Assuming that the traffic is the same in both directions, is it possible to determine the number of cars that pass along the highway per hours? (You may assume that the velocity of a car can take only two values.)