- #1

Alexsandro

- 51

- 0

You are lost in the National Park of Bandrika. Tourists comprise two-thirds of the visitors to the park, and give a correct answer to request for directions with probability 3/4. (Answers to repeated questions are independent, even if the question and the person are the same). If you ask a Bandrikan for directions, the answer is always false.

(a) You ask a passer-by whether the exit from the park is East or West. The answer is East. What is the probability that is correct ?

(b) You ask the same person again, and receive the same reply. Show the probability that it is correct is 1/2.

(c) You ask the same person again, and receive the same reply. What is the probability that is correct ?

(d) You ask for the fourth time, and receive the answer East. Show that the probability it is correct is 27/70.

(e) Show that, had the fourth answer been West instead, the probability that that East is nevertheless correct is 9/10.