04-04-2005, 01:17 PM | #1 | ||
Pro Rookie
Join Date: Oct 2000
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Puzzle: Russian Roulette
I saw this on another board and thought I would post it here. The concept should seem familiar to most of you. The standard disclaimer applies. This is not my puzzle, yada yada yada. This may be very easy for some of you, but here goes.
You and a friend are playing Russian Roulette with a standard 6 chamber revolver. You place two rounds in adjacent chambers and give the wheel a spin. You give the gun to your friend and he pulls the trigger. Click. He hands the gun to you. You have a choice. You can spin it again, or you can simply shoot the next chamber. Does it matter which one you choose? If it does, why? Last edited by primelord : 04-04-2005 at 01:17 PM. |
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04-04-2005, 01:21 PM | #2 |
Head Coach
Join Date: Oct 2000
Location: North Carolina
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I would pull the trigger without spinning. I'll leave my reasoning, however, so as not to spoil it for others (on the chance that I am right).
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04-04-2005, 01:23 PM | #3 |
Coordinator
Join Date: Oct 2000
Location: The Black Hole
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I agree. The possibility that your buddy pulled the empty chamber next to a loaded one is less than the possibility he pulled an empty chamber next to an empty chamber. Not sure how the numbers work out, but that's my reasoning.
Also, I wouldn't play this game. |
04-04-2005, 01:27 PM | #4 |
General Manager
Join Date: Oct 2004
Location: New Mexico
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I break it down like this:
The first shot had 2/6 chances to be fatal. Without spinning, the second shot now has 2/5 chances to be fatal. Spinning it again leaves you with 2/6 chances. Although the bullets are adjacent... how does that change the probabilities? 1. ----bb 2. ---bb- 3. --bb-- 4. -bb--- 5. bb---- 6. b----b So the first 'empty' shot had to be either 1-4. 1. ---bb- 2. --bb- 3. -bb-- 4. bb--- So actually, there is a 1/4 chance that shot 2 will be fatal... I conclude you are better off NOT spinning. |
04-04-2005, 01:30 PM | #5 |
Coordinator
Join Date: Oct 2000
Location: The Black Hole
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Hey also, why would my buddy let me spin for him? If it were me, I'd definitely be spinning it myself.
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04-04-2005, 01:31 PM | #6 |
Retired
Join Date: Oct 2000
Location: Fantasyland
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Agreed. Pull the trigger without spinning.
If you don't spin, the 2nd bullet is immaterial. For all intents and purposes, it doesn't exist because it cannot fire withou the first bullet firing. Once the friend pulled the trigger, there's 3 empty spaces left and 2 bullets. But remember the 2nd bullet cannot fire without the first - therefore, it doesn't exist. Without getting too deep into statistics, for me that's a chance of 3 empty spaces and 1 bullet = 25% of a bullet. Spinning the barrel and starting over means there's 4 empty spaces and 2 bullets = 33% change of a bullet. I may not be correct, but that's my reasoning. Of course, I'd turn the gun on my friend and unload the other 5 chambers on his ass for asking me to play such a stupid game. |
04-04-2005, 01:34 PM | #7 | |
General Manager
Join Date: Oct 2004
Location: New Mexico
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Quote:
I actually think this is the correct answer. Aim for the chest, unless he's wearing body armor. |
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04-04-2005, 01:37 PM | #8 |
Pro Rookie
Join Date: Oct 2000
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I figured this might be fairly easy for you guys. You are correct pulling the trigger without spinning is the correct answer. And the math shown here is correct. You have a 25% chance of the next chamber being a bullet where as with a spin you have a 33% chance of running into a bullet.
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04-04-2005, 01:48 PM | #9 | |
Head Coach
Join Date: Oct 2000
Location: Green Bay, WI
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Quote:
But if the second bullet doesn't exist until the first one's fired, doesn't that actually make it a 20% chance? (I'm joking, of course) |
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04-04-2005, 01:52 PM | #10 |
Grizzled Veteran
Join Date: Jan 2005
Location: Appleton, WI
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On a board like this with all of the poker talk going on, I would imagine any probability question would be answered pretty quickly.
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04-04-2005, 02:01 PM | #11 | |
lolzcat
Join Date: Oct 2000
Location: Annapolis, Md
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Quote:
Actually, the history of probability puzzles here substantiallty predates the poker outbreak. Some of my favorite probability puzzles from this forum: (at least the ones still standing, not lost to the cyber-ether) Monty Hall, revisited – probably its third or fourth offering here, but a nice discussion Monty Hall in Parade magazine – any chance to beat up on Marilyn works for me The infamous flush puzzle – can’t be revived, but quite a discussion about probability (and in the end, semantics) |
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04-04-2005, 02:32 PM | #12 |
Grizzled Veteran
Join Date: Jan 2005
Location: Appleton, WI
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Some very interesting reading in there.
With all of the poker talk that has popped up, do you think a discussion like those you posted is still possible? I suppose in a different context, the formulation of the actual probability problem could still be open for discussion. |
04-04-2005, 02:44 PM | #13 | |
Head Coach
Join Date: Oct 2000
Location: North Carolina
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Quote:
Yes. If someone came to this board and started posting difficult, but not impossible, puzzles, I think that there would be a group ready, willing, and able to engage in that kind of discussion. The problem, of course, is coming up with the puzzles. |
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04-04-2005, 02:56 PM | #14 |
Banned
Join Date: Jul 2002
Location: Placerville, CA
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It's simple, really. I spent the last few years building up a resistance to iocane powder.
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04-04-2005, 02:58 PM | #15 | |
General Manager
Join Date: Oct 2004
Location: New Mexico
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Quote:
You only think I guessed wrong - that's what's so funny. I switched glasses when your back was turned. Ha-ha, you fool. You fell victim to one of the classic blunders, the most famous of which is "Never get involved in a land war in Asia", but only slightly less well known is this: "Never go in against a Sicilian, when *death* is on the line.". Hahahahahah. |
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04-04-2005, 02:59 PM | #16 |
lolzcat
Join Date: Oct 2000
Location: Annapolis, Md
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The enigma puzzles, it seems, have largely turned into cryptpgraphy and crossword-style clues... I guess that style of puzzle just fits the genre better. But we have had our fair share of puzzles in these parts. Quite a few involving probability, too... always a rich subject.
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04-04-2005, 03:00 PM | #17 | |
Grizzled Veteran
Join Date: Jan 2005
Location: Appleton, WI
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Quote:
Yes, thinking about it more, the puzzle isn't in the probability calculations, but in the setup of the problem. Forget I said anything. |
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04-04-2005, 03:06 PM | #18 | |
Coordinator
Join Date: Jan 2002
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Quote:
- Dead silence - The poster making several sad bumps of his own post - Several people pointing out that there won't be any response because the puzzle is too difficult - Some half-hearted attempts to solve the puzzle - Someone getting answer, and posting the entire thing immediately to prove how smart they are - Several people pointing out that the puzzle was too easy - Dead silence - Complaints that nobody ever posts any puzzles
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04-04-2005, 03:09 PM | #19 |
lolzcat
Join Date: Oct 2000
Location: Annapolis, Md
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I'm willing to take that risk. Maybe we can revive an old favorite...
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04-04-2005, 06:46 PM | #20 |
College Benchwarmer
Join Date: Nov 2003
Location: New York
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Real men play RR with 5 bullets, and only one empty chamber.
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In the immortal words of a great alcoholic, "Can't we all just get along?" |
04-04-2005, 10:22 PM | #21 | |
Grizzled Veteran
Join Date: Jan 2005
Location: Appleton, WI
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Quote:
Sure, real dead men. |
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