It’s the Friday Puzzle!

44

coverPlease do NOT post your answer, but do say if you think you have solved the puzzle and how long it took. Solution on Monday. This puzzle was kindly sent to me by Vlad G.

Three men decide to have a shooting contest to the death. Each man has one gun, and each gun contains just one bullet.  They draw straws to determine the order in which they will shoot. The rules are simple:
If the first man to fire shoots the second man, then the third man has to shoot the first man. If the first man to fire shoots the third man, then second man has to shoot the first man.  Oh, and the first person has to shoot.
What should first man do to ensure that he survives the contest?

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle(UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.

44 comments on “It’s the Friday Puzzle!

  1. You Tube Wannabe says:

    SPOILER ALERT
    Should he find a better puzzle website?
    BTW 1 second

  2. Andy says:

    This was on Dara O’Briain’s programme the other week. Won’t spoil the answer though!

  3. Obvious! I only hesitated for a few seconds because I couldn’t believe how easy and obvious it was, and I needed to re-read it to double-check.

  4. Tony says:

    Remember this from an old QI. Nice puzzler if you haven’t heard it.

    BTW tired of people criticising quality of puzzles. They’re fine general teasers which is exactly what I need. Keep them coming Mr Wiseman ( or is it doctor..?!)

  5. Anonymous says:

    I don’t know where to start on this one. I haven’t got a clue.

  6. Anne Elk says:

    Couple of seconds.

    I’m with Tony – there’s no need to criticise the puzzles. If they’re too easy for you go somewhere else. We’re not supposed to be re-sitting our Finals every Friday morning; these are puzzles for general entertainment. Some are simpler than others, of course they are.

    • You Tube Wannabe says:

      I’m with you and Tony on this one Anne. There is no need to criticise the puzzles.
      Btw what sites do you recommend for more challenging questions?

    • Canadian Atheist (calm down girls, form an orderly queue) says:

      Anne
      You need to high tail it over to Richard’s answer posted on Monday 27/5/13. It is a maelstrom of unfair criticism of Richard’s excellent brain teaser.

  7. ivan says:

    I don’t understand the contest rules: it doesn’t appear to distinguish between hits and misses, and it doesn’t explain what happens with the 3rd gun. It may not matter, and while I can think of a solution (instantly) where it doesn’t matter, I somehow doubt it is the intended solution.

    • ivan says:

      OK I now see what I misunderstood. The drawing of straws gives a 1, 2, 3 order of shooting, not merely an identification as man 1, man 2, man 3 for the application fo the further rules. The additional rules do not over-ride that, except to the extent that someone is already dead. If “shoots” => “kills” then there is no need for these additional rules, so plainly that implication is not present.

  8. Fun. I thought of two obvious choices, but neither seemed to guarantee that the first man would survive. I’m intrigued to learn the answer on Monday.

    • Berhard says:

      same with me, .. two obvious solutions would like to now if they are the same.. looking forward to monday…

  9. Dave's Neighbour says:

    Is the first man obliged to aim at the second man?. Is he for example free just to fire up into the air?

  10. Hugh Jarse says:

    Or, maybe put the gun to his own head?! That’ll confuse the other two buggers!

  11. Julia says:

    what a fun contest! I got Dave’s Neighbour’s solution, then I re-read the question. Now I’ve got a clever puzzle solution. I’d still pick Dave’s Neighbour’s way if it were me though.

  12. Darth Vader says:

    Han shot first.

    (Google this if you want to know the connection to this question)

  13. Anonymous says:

    Took me a minute, but I have a guaranteed survival answer. The rules are quite vague though, so it might not be the same as the official answer.

  14. Anonymous says:

    Run away!

  15. Lazy T says:

    If I had to shoot first I’d hold the gun to no.2’s head and steal his gun, do same to no.3 declare the contest null and void and have a nice smoke.

  16. Zbird says:

    I like Hugh Jarse solution

  17. Mark_D says:

    I think the solution involves Iocane Powder, a giant, and a duel, but I’m not sure.

  18. Jefferson says:

    I’ve seen the puzzle before and know the answer. Can only say that the solution relies upon shooter 2 making a rational choice. Therfore, a safe outcome for shooter 1 is a high probability, but not guaranteed. Then again. What sort of rational person would engage in this type of contest to begin with?

    • ivan says:

      The other thing we are not told, and which is important for this, is how reliably or accurately these people shoot. It also depends upon the exact meaning of “shoots” someone in the rules.

  19. Physicalist says:

    I see a couple obvious boring solutions, but am not seeing the clever interesting solution that would make this count as a puzzle.

  20. John says:

    Are these the same 3 men that stayed at the hotel and the bellboy took out the tip ?

  21. Seemed/seems pretty obvious, but I look forward to Monday to seeing if my theory is correct.

  22. Anonymous says:

    Is it just me – or do the puzzles recently seem more fitting for Elementary School students?

    Solved by the time the last word was read.

  23. Gus Snarp says:

    I’ve got four answers that all work. Not sure if I should keep working to see if there’s a different kind of solution.

    • Another Elk says:

      Would you now post your four answers please Gus?
      Richard’s answer on Monday falls far short of adequate.
      Thanks

  24. One Eyed Jack says:

    This is one time you should definitely bring a knife to a gun fight. You don’t have to reload a knife.

  25. fred lemming says:

    Thirty Seconds. Hadn’t read/seen this one before.

  26. Greg says:

    Well I can’t get this one. I’m confused. Maybe I’m reading it wrong.

  27. Anonymous says:

    Really.. If they’re too easy or you’ve seen it before, go somewhere else. Stop complaining! Or if you can do better yourself, start your own smarter than everyone else website!

  28. Henry says:

    There’s the Logic Way, the Die Hard Way and the Mystery Novel Way to solve this puzzler. Do we get credit for all three?

  29. ctj says:

    interesting. while i can think of several approaches that increase #1’s likelihood of survival, i can think of none that meet the puzzle’s condition that #1 “ensure that he survives the contest.”

    • ctj says:

      i should add that since this isn’t a rational contest (what rational person would ever “decide to have a shooting contest to the death”), we cannot assume that #2 or #3 are rational actors.

  30. You’re right, ctj, the word “ensure” is too strong a word here. I would say, “What should the first man do to give himself the best chance to survive the contest?”

    • Anne Elk says:

      I think ‘ensure’ is fine in this context. We are only given one set of very simple rules. If Gunman 1 fires into the air, the rest of the rubric is null and void. The other two can’t shoot him. It doesn’t matter what would happen in *real life*: by the rules of the puzzle, the guy’s safe.

  31. Greg says:

    Ok, I’ve got it now. It was actually my first thought but couldn’t justify why it was the right answer until now. There are some hints in comments above.

  32. Anonymous says:

    great!

  33. sergio says:

    good!

  34. I am not sure where you are getting your info, but great topic. I needs to spend some time learning much more or understanding more. Thanks for wonderful information I was looking for this information for my mission.|

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