Question 30
When I drive to school every day, I pass eight traffic lights, each either green, yellow, or red. I find that, because of synchronization, a green light is always followed immediately by a yellow, and a red light is never immediately followed by a red.
Thus a sequence of lights may start with GYRY, but not RRGG.
How many possible sequences of the eight lights are there?
AI clarification for this edition: apply the restrictions only to adjacent pairs within the eight-light record; the last light may be any colour.
Thus a sequence of lights may start with GYRY, but not RRGG.
How many possible sequences of the eight lights are there?
AI clarification for this edition: apply the restrictions only to adjacent pairs within the eight-light record; the last light may be any colour.