There are 5 cars in a car dealer and 5 keys. The sales person doesn't know which key is for which car. If assign 5 keys to each car, which one below is impossible as the number of cars that will have the right key?
If 4 cars have their right key, it remains 1 key and 1 car. The key remaining is for the remaining car. In this situation 5 cars have the right key, so 4 is impossible.
