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 Cars on the road (Posted on 2004-04-09)
If the probability of observing a car (read: at least one car) in 20 minutes on a highway is 609/625, what is the probability of observing a car (read: at least one) in 5 minutes (assuming constant default probability)?

 Submitted by SilverKnight Rating: 2.5000 (4 votes) Solution: (Hide) If the probability of seeing a car is 609/625, then the probability of NOT seeing a car is 1 - 609/625 = 16/625. This means that if we must not have seen a car in each of FOUR five minute periods. So we must multiply the likelihood of NOT seeing a car in each five minutes, x (4 times) and get 16/625. x^4 = 16/625 x = 2/5 Since the question asked about the likelihood of SEEING a car in 5 minutes, we must subtract that likelihood from 1... 1 - 2/5 = 3/5, the answer. ___________________________ Problem found at: http://www.techinterview.org/Puzzles/carsontheroad.html

 Subject Author Date Solution To The Problem K Sengupta 2007-04-17 11:35:26 puzzle solution K Sengupta 2007-04-17 11:29:00 hmm ofnoconcern 2004-11-28 15:19:55 Alternative to Poisson Charlie 2004-04-10 14:17:42 re(6): One Mean Poisson = Shark Penny 2004-04-09 21:53:52 re(5): One Mean Poisson = Shark Richard 2004-04-09 21:35:36 re(4): One Mean Poisson = Shark Penny 2004-04-09 21:19:04 re(3): One Mean Poisson = Shark Richard 2004-04-09 21:13:53 re(2): One Mean Poisson = Shark Penny 2004-04-09 19:28:46 re: One Mean Poisson = Shark Larry 2004-04-09 19:16:04 One man's Mean is another man's Poisson Penny 2004-04-09 16:01:24 Solution Rajat 2004-04-09 15:37:15 re(4): Auto-suggestion ThoughtProvoker 2004-04-09 15:31:28 re(3): Auto-suggestion Charlie 2004-04-09 14:50:43 re(3): Auto-suggestion Richard 2004-04-09 14:28:47 re(2): Auto-suggestion ThoughtProvoker 2004-04-09 13:43:53 re: Auto-suggestion Charlie 2004-04-09 13:38:18 Solution Jer 2004-04-09 12:13:22 Auto-suggestion Penny 2004-04-09 12:01:02 answer Ady TZIDON 2004-04-09 11:17:28

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