Interview Questions And Answers 
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Lets play a game of Russian roulette. You are tied to a chair and can,t get up.Here is the gun , six chambers all empty. Now I put two bullets in the gun and I put these bullets in the adjecent chambers. I close the barrel and spin it. I put the gun to your head and pull the trigger. Clik and the slot was empty. Now before we start the interview I want to pull the trigger one more time , which one do you prefer , that I spon the barrel first or that I just pull the trigger ?
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shoot without spinning. if the barrel is spun, the chance of being shot is 2/6 = 1/3. if it is not spun, there is only one position out of 4 that would lead to being shot, so that chance in this case is 1/4.
since 1/4
Chance of being shot when gun is spun :2/6 =1/3
Chance of being shot when gun is not spun :2/5
your call
Shoot with spinning.
If the barrel is spun, the chance of being shot is 2/6 = 1/3. if it is not spun, there are two positions out of 4 that would lead to being shot, so that chance in this case is 2/4 i.e 50%.
That’s not correct.
If you don’t spin the barrel you will have 2/5 (40%) chances to get killed.
So, it’s better to spin it because than the chances of being killed are only 2/6 (33%).
um no
it is actually only a 1/6 chance if not spun. Basically you needed to be on the spot two away from where the bullets begin (you know they are next to each other). Thus it is 1/6 if not spun,
2/6 if spun…
I think
Let the russian guy answer
When the gun is spun - the chance of being shot is 1/3, correct. Right after the gun is spun and the cell is empty - this is a little bit more complicated: There are 4 positions possible:
1. right after a pair of bullets,
2. one after the pair of bullets,
3. the one cell before the bullets,
4. right in front of the bullets…
It means that we have 1/4 of being shot, if not to spin.
If you don’t spin the barrel we know that 2 chambers are accounted for. 1 chamber that was just fired and empty. 1 chamber that has a bullet next in line to the one that would have blown your head off (remember, two bullets adjacent). With this logic, 2 of the 6 are accounted for which leaves a 1/4 chance of death equaling 25%.
If you spin the barrel, none of the chambers are accounted for. You now have a 2/6 chance of death equaling 33.3%.
Answer; just pull the trigger without spinning.
I don’t believe it matters if the bullets are adjacent, nor the number of bullets in the gun. It only takes one to kill you, after all, so I think that’s a red herring.
Every time you pull the trigger you reduce the odds. So first is 4/6, second is 3/6, third is 2/6. If you spin the barrel the odds are always 4/6. If you’re Jack Bauer, you’ll shoot the guy who made you play this game.
Since the trigger was already pulled once and the bullets are adjecent, there is a 1/4 chance of being killed if you don’t spin. If the barrel is spun, you are back to a 1/3 chance.
Duncan is completely right. The catch is in the term ‘adjacent’. If it were not adjacent bullets then the prob will change from 1/4 to 2/5 and in that case spinning is a good choice. But as of the given statement spinning is poor as it raises the chances being shot. Enjoy.
Position of the bullets matter!!
Let X be a bullet.
(a click moves the trigger 1 position to the left)
X _ X _ _ _
1 2 3 4 5 6
First, fired and missed — Hence, fired either 2, 4, 5, 6.
For next one to miss, first one should have been — 5, 6 (33.33% chance it was 5 or 6)
For next one to hit, first one should have been — 4,2 (33.33% chance it was 2 or 4)
The other 33.33% chance is that it fired a bullet, which never happened.
For the second click, the only positions remaining are 1,3 or 4,5.
1,3 means hit, whereas 4,5 means miss. So, in the second click, there is 50% chance of hit (or miss).
Whereas if you roll the barrel, chance of being hit is 2/6 or 33.33%.
Hence, by rolling the barrel again, there is a smaller chance of being shot.
This is also instinctive: every time there is a miss, the chances of the next one being a hit will increase.
the interviewer just said he “wanted” to pull the trigger one more time, and asked if you would like him to pull the trigger or spin. i’d choose for him to spin. the odds of getting killed if he shoots is 2/5. the odds of getting killed if he spins are 0. I would want a drink before this interview but that doesn’t mean i’m getting one, as the interviewer wants to pull the trigger one more time, but asks if you want that or not. duh…
Its incorrect to take the 2/6 and 4/6 ratio, as adjacent would just mean that you have 5 bullets in a gun with 5 chambers.
When the bullet has been shot once, and you aren’t killed, there remain only 3 possible combinations in all, and out of those 2 are favourable that you won’t die.
That makes 2/3=66.7% chances if the guys shoots again without spinning.
If its spun, the number of arrangements would be 5, and the ones in which you won’t die would be 3.
That makes 3/5=60%
So, its more likely to save your life in case the barrel is shot again without spinning. What say, guys?
Its incorrect to take the 2/6 and 4/6 ratio, as adjacent would just mean that you have 5 bullets in a gun with 5 chambers.
When the bullet has been shot once, and you aren’t killed, there remain only 3 possible combinations in all, and out of those 2 are favourable that you won’t die.
That makes 2/3=66.7% chances if the guys shoots again without spinning.
If its spun, the number of arrangements would be 5, and the ones in which you won’t die would be 3.
That makes 3/5=60%
So, its more likely to save your life in case the barrel is shot again without spinning. What say, guys?
1. not spin, one out, five unknown position left,
10 combinations (5*4/2) and only 6 of them are good (4*3/2)
chance to stay alive 6/10 = 3/5
2. spin it, the same as it was the first time, 4/6 = 2/3
2/3 > 3/5
SPIN AGAIN,
Imagine halving the scenario (1 bullet, 3 chambers)
- No Spin, chances of getting shot 1/2
- Spin, chances of getting shot 1/3
This is not that complicated. X being a bullet, _ being and empty chamber. The gun rotates from 1 to 6, and the bullets are in adjacent chambers.
The setup: _ X X _ _ _
1 2 3 4 5 6
The interviewer just got a blank, so the current position must be 1,4,5, or 6. If it’s 1, the next one is a bullet. If it’s 4-6, the next one is empty. So if the interviewer just fires again, you have a 1/4 chance of getting shot.
If, on the other hand, the interviewer spins again, you’re back to the initial 2/6 or 1/3 chance of getting shot.
I’ll take the 1/4 chance, myself.
Don’t spin. (Keep reading only if you want to read what others have said being said another way.) All you care about is whether the next chamber has a bullet. Let’s say the interviewer just dry-fired chamber 1. The only possibilities left for where the remaining bullets are chambered are chambers 2&3, 3&4, 4&5 and 5&6. The only fatal combination is the first one. Therefore you have 3 out of 4 chances to live, or 75%, if the interviewer pulls the trigger now. If he spins the barrel there is a 2/6 chance of landing on the fatal chamber, or a 66% chance of landing on an empty one. Therefore the odds are better if he doesn’t spin.
Probability to be saved
Without spinning: 2/3 = 66.67%
With spinning: 4/6 = 2/3 = 66.67%
So either is fine.
x
- x
- -
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This is the case. The gun is shot once. This shot may be one of those 4 dashes. So, let’s see the probability for not spinning it again:
This first shot should have been the top left empty chamber (1/4, since we know it was empty) OR the one under that (1/4 again) OR the bottom-most one (1/4). In these cases everything is fine for you which adds up to be 1/4 + 1/4 + 1/4. And if it is the right most empty chamber, you are not happy (1/4). So the possibility you will die is (1/4)/(3/+) = 1/3.
With spinning it is obvious that the probability is 2/6 = 1/3.
So, they are both the same. Just relax and say, doesn’t matter.
The question is if the person wants to pull the trigger or spon the barrell.
Whatever calculations, combination and permutions you do, you never know that the current barrel does have the bullet or not and there is no way unless the person with gun allows you to check.
If the trigger fires the bullet, you would not have chance to prove your step.
So think again guys, instead of doing calculations, probably skills in Martial arts would help you put down the bad man before he pulls the trigger.
Seems to me if we’re playing Russian Roulette, the next time the interviewer pulls the trigger it should be pointed at his head, not mine. I don’t care whether he spins first or not. Maybe I’m being too practical.
don’t spin
there are six possible arrangements at the start
x….x A
xx…. B
.xx… C
..xx.. D
…xx. E
….xx F
after we know an empty chamber was first, A,B can be ruled out. Hence, it muxt be one of C,D,E,F. Only C has a bullet in the second chamber. chance of death: 1/4
if one spins, presumably all A..F are equally likely. A,B are deadly, others are safe. chance of death: 1/3.
This is so simple I cant believe there is such debate about this. Look, it comes down to unknowns. Even after you spin and pull the trigger the first time, you have no idea where the two adjacent bullets are, its impossible to tell without looking in the barrels. The only thing you know for sure is that it is not that barrel.
We all agree that the first spin is 2/6 chances of being shot, because there are 2 bullets and 6 chambers.
If you shoot once, and don’t die, that means that you now have accounted for an unknown (lost a safe spot) and still have 2 chances to die. Hence 2/5 chances to die.
Remembering the fact that a smaller chance to die is better for you, it is simple to see that you want to spin again, to give yourself another unknown.
The problem is of conditional probablity.
Given that the bullet did not fire the last time, we have two situations.
Either the bullet will fire this time OR the bullet will not fire this time.
For the bullet to fire second time, 1 out of the 4 empty chambers must have been selected.
So the probabliy of being killed the second time, given that the barrel is not spun again and also given that the last time I was not killed = 1/4 = 25%
And in case the barrel was rotated, the probablity of being killed = 2/6 = 1/3 = 33.33%
So I choose that the barrel be not spun again.
dont spin. ignore the fools. this is a counting problem- the people who say spin aren’t counting the odds properly.
A shot is fired and it turns out the chamber is empty. Now I feel i am left with 4 possibilities.
If 0 -> not loaded
1 -> loaded
1. The next three chambers are empty
00011
2. The next couple of Chambers are empty
00110
3. The next chamber is empty
01100
4. The next couple of chamber’s are loaded
11000
note: 10001 is not possible because the last chamber was empty.
so according to my assumption, the probability of me being safe is 3/4 which is 75%
Now if i spin, the probability of me being safe is
4/6 => 2/3
Which is 67%
so allan says ->
and i have confessed…:-) so… Pls….
DONT SPIN, give it to the interviewer, close ur eyes and say, jesus christ, am sorry for all that i’ve done.. But i love u…
Explanation
X X _ _ _ _
1 2 3 4 5 6
When he fired, position should have been any of 3 ,4,5,6
had it been 6, he will get hit next time , otherwise not ie , out of 4 new positions 4 ,5, 6 ,1
chances that he get hit is in pos-1
ie 1/4 (25%)
If he spins chances that he get hit is 2/6 = 1/3 (33%)
So he should go with out spinning
Shot without spinning…
consider that out of the 6 chambers 2 are placed consecutively… But the first shot has missed.. So here there is no need abt the second bullet since for gettin shot by the second bullet requires that the first bullet has to be shot… So out of 6…
One has been shot(missed one)
One has 0 probability(the second bullet)
So the probability of being shot is 1/4
But if the barrel is spun ..
then out of 6 positions 2 are dangerous…
So probability of being shot when it is spun is 2/6=1/3
So shoot me now.. Dont spin..
Shoot witout spun ……
Shoot without spun, probablity of bullets position as first shoot is empty(1 represents bullts position)
011000
001100
000110
000011
Out of above 4 options bullet will be fired in only one case(First case). Probability 1/4 (25%).
And with spun
110000
011000
001100
000110
000011
100001
So in this case probabilty of being shoot in each case is 2/6(33.33%).
Your turn mate… shoot with spinning in the opposite direction.
Let me give it a “shot”.
Given:
1. a sequence of 6 barrels. Let assume is lay down as:
1,2,3,4,5 and 6
2. it’s a round barrels, so if we lay these in a “circle”, then the barrels are lay as above but barrels 6 and barrels 1 are adjacent. It’s similar to a “circular” list.
3. the 2 barrels that contains bullets are adjacent to each other.
4. one shot is empty
Logic:
If it is a *circular* and has *2 adjacent*barrels with bullets. Regardless which 2 adjacent barrels, you choose to put the bullets in, I will also have 4 adjacent barrels that are empty (total 6 barrels and it’s a circular…remember !?).
Let pick *any* 2 adjacent barrels with bullets, say 5 and 6 for the sake of discussion. the list above would have
adjacent 1,2,3,4 are all empty
adjacent 5 and 6 have bullets.
**ASSUMPTION: the barrel is rotating clockwise and in a circle ie. the rotating order 1->2->3->4->5->6->1 (circular)
From (5) above, 1 shot is empty.
Notice that if the first shot is “empty”, there is *ONLY ONE** chance for the next shot to have bullet is that the last “empty” shot was (or MUST BE) at barrel #4. And, there are 5 barrels left.
So, without spinning, the chance to get shot in the next trigger is 1/5
If we spin the barrels before the next trigger, the next shot could be any of the 6 barrels. There are 2 barrels with bullets
So, with spinning, there are 2 out of 6 chance to get shot –> 2/6 = 1/3
As the result, I would choose the next trigger *without* spinning.
Spin the barrel. Probability of getting killed in this case is 2/6. in the other case probability is 2/5.
The explaination submitted by “Thanh the man” from Seattle is the most clear to understand and accurate. I was about to write the same.
Don’t spin Increase ur chances ..Let me explain…
Case 1 : simple ….you spin. now we have 2 bullets out of 6 chambers and any one can come . So prob of being hit is 1/3 =33.33%
Case 2 : one empty slot has been wasted.
now most ppl say prob 2/5 but that is wrong….
Bullets are in circular say 1 2 3 4 5 6.
2x 3x
1- 4-
6- 5-
now since one fire has taken place. let us see the possible positions of trigger.
trigger can be at position 1(empty) assuming last fired was 6
Hence bullet hit chance is 25% which is less
so don’t spin
trigger at 2(bullet) assuming last lired at 1(empty)
trigger not possible at 3 as for that last fired (2) has bullet.
trigger not possible at 4 as for it last fired (3) has bullet.
trigger possible at 5(empty) as last fired can be 4 (empty)
trigger possible at 6(empty) as last fired can be 5 (empty)
newt at 1 is the first case…
There is a joke about technical directors (VP’s in good old USA).
Three company directors setup an enterprise in a country which is taken over by a new regime. The new regime sentence all overseas directors to death by guillotine. According to the law of the land if the executioner can’t kill you, you are set free. The MD (CEO) walks up, head in the block, executor pulls the cord to release the deadly blade, nothing happens after fifteen minutes of trying, the MD is set free. The sales director walks up, head in block, same thing and is also let free. The Technical Director walks up, execution pulls the cord, nothing happens, Technical Director churps up, “whats that wedge doing in the wheel pulley?”
Don’t give the answer to a question that might kill you. The answer to this question is to not to respond with an answer. If you want to be smart, then it’s “I can’t decide between a risk of 2/3 and 3/4, the odd are just not good enough, we’ll come back to when i have worked out a 100% chance of living, lets move on and we’ll come back to this one.”
But I wouldn’t recommend being smart, when asked, just respond with “I’m thinking about it.” Work on your hand ties, throw the interview desk on them, grab the gun and offer the interviewer the option! The right move, might be to just away from an employer that asks this stupid question, its only a job afterall and they are suggesting putting you in a situation that may kill you. Bad, capital B. Very unprofessional.
my answer would be - spin the barrel… as mere spinning of the barrel wont kill me… so can we now start with the interview
Dont spin!
Let me take the liberty of tweaking the problem a bit. Let’s try and answer two questions.
There’s this loaded gun with two bullets in adjacent barrel, nicely spinned. Now,
1. What is the probability of your survival if I fire two consecutive shots (basically a single event)?
2. What is the probability of your survival if I fire one shot and then fire another shot after spinning (two independent events)?
Answer to the first question will be 3/6=0.5 since there are only 3 safe barrels out of six that would leave you alive after two consecutive shots.
Answer to the second question is 4/6*4/6 = 0.444
Clearly your chances of survival are greater in the first case, i.e. shooting without spinning.
Don’t spin. Here’s the simple explanation:
You know that the last shot didn’t fire, therefore the gun was in one of the four empty slots. If you don’t spin, the barrel will rotate to the next spot. If you look at the next slot for each of the four empty slots of the previous shot, only one of them contains a bullet. Therefore, the probability if you don’t spin is 1/4.
If you spin, the probability is 2 bullets in 6 slots, or 1/3.
If we do not spin the barrel, the slot may or may not have a bullet. so, the chances of getting shot is 1/2.
If we spin the barrel, the chances of getting shot is 2/6 = 1/3.
Either way chance of getting shot is 1/3. So if you spin or not does not matter.
Ok we all agree when the gun is spun the chance of being shot is 1/3
F E
A D
B C
Lets assume the bullets are on the AB positions. There are few possible barrel positions you can end up, after the first time pulling the trigger (and if you are still alive):
Position D, E, F and A. However you do not wanna be on the position A. so that leave three positions out of four in your favour. So the chance of being shot = 1/4.
Don’t spin.
We all agree that if you spin there is a 1/3 chance of being killed.
Since the bullets are in adjacent chambers, you have four possibilities when your first pull is on an empty chamber:
1. There are 3 empties before the next bullet.
2. There are 2 empties before the next bullet.
3. There is one empty before the next bullet.
4. The next chamber is a bullet.
So the odds if you do not spin are 1/4, which gives you a 75% chance of survival vs. 67% for spinning.
2
1 3
4 5
6
Let this be the gun. Assume that 5 & 6 hold the bullets. Now,
the first shot didnt fire. that means the position could have been in 4, 1, 2 or 3. After the first shot, current position would be 1,2,3 and 5(in that order assuming that the position might have been in 4, 1, 2 or 3). Out of these 4 positions only one position has the potential to fire a shot. So probability of getting shot in second shot is 1/4 or 25%.
Now, if we spin again, the probability that a potential position will come is 2 out of 6 positions. ie 2/6 or 33.3%
Obviously choosing the gun without spinning is good for life!!
Chance of being shot when gun is spun :2/6 = 33%
Chance of being shot when gun is not spun : 3/6 = 50%
Explanation
_ _ _ _ X X
1 2 3 4 5 6
Presume we have bullets in the 5th an 6th chambers. After one spin the chance of positioning on chambers 1,2 or 3 is 3/6=50% => after 2 shots, you’re still alive.
dont spin
in simple terms
with the first you lost one possibility of a win but also a loss. so there is one less shot because they are consecutive. i will take 1/4 over 1/3 any day
When spun, chances of escape is 4/6 = 66% and chance of death is: 2/6 = 33%. When not spun, chances of escape is 3/5= 60% and death is 2/5= 40%. SO SPIN IT
When he pulled the trigger, since you did not get shotted, he eliminated one possibility, an empty chamber. But you can also eliminate the second chamber with the bullet since it would have meant you would have been shot in when he pulled the trigger.
That leaves 4 possibilities with only one chamber having a bullet. So if he does not spin again the odds of getting shot are 1/4. If he spins the chamber again the odds of getting shot are 1/3.
Don’t spin the chamber.
I say spin.
Everyone agrees that your chances of dying from the first trigger pull after a spin is 1/3.
For the case of whether to spin again I say rephrase the question: “what are the odds after a spin that, if the trigger is pulled twice, the gun will fire at least once?” Since there are 3 out of the 6 starting positions where the gun will fire at least once in 2 pulls there is a 50% chance of dying if you don’t spin.
By the first trigger pull you have gained knowledge about the state of the gun - not exactly where the bullets are, but some information you can be sure about.
The second bullet CANNOT fire on the next shot, because if it were lined up to fire then the first trigger pull would have fired the first bullet and killed you already - which it did not. The empty chamber from the first trigger pull will not be the next one either.
So while you don’t know if the first bullet will be the next shot, you do know that there are four chambers that can possibly fire and the first bullet only fills one of them. Thus 1/4 or 25% odds of dying if you don’t spin, and back to 33% odds of dying if you do spin. So don’t spin.
After the first shot, there are only four possiblities left. The chance of being shot again is 1/4.
O O O O
X O O O O O O X
X O X O O X O X
O X X O
What about Science as in Newton, the apple… gravity not only math / probability? Given revolvers are finely machined, when you spin an empty cylinder probability alone is a fair guestimate as to whether you should spin or not because gravity is not influencing the final disposition of the cylinder.
However if you place two 158 grain (not including the weight of the casing and powder) rounds in adjacent chambers and spin again the same manner as previously, probability and gravity are likely to place the rounds at the bottom with the barrel at the top. If the cylinder is closed in the same fashion and the trigger squeezed the double action revolver will advance the chamber one position therefore most likely to have an empty chamber advance to the barrel position a second time in a row if the cylinder is spun.
Even if I could calculate the right answer, which I can’t, I would not give it as an answer to the shooter. Why be complicit in risking your life? This is game you don’t want to play. If you are forced to play, and you do not get shot, you will be forced to play a riskier game, until you ARE shot. This is like Sophie’s Choice (where a Nazi asks a Mom in line at Auschwitz with her two children which one should be shot; she is told they will all three be shot if she can’t decide, and fast. So she picks one. There is no assurance that the creep who gave her this deal will save the life of anyone. And once she has given up the one child, she must be tortured all her life for the decision, no matter which one she gave up). When people ask you to play such games, being servile and going along with it, thinking that your IQ will help you, is wrong. JUST SAY NO, on principle, even if it means you will be hurt or die.
Clearly by now we all know the answer is to NOT spin. Spinning the barrel provides you with another 33% chance of being shot (2/6). Those who took the approach of re-phrasing the question to be what are the odds of surviving if you pulled the trigger twice after spinning are missing the point that we have gained knowledge after the first trigger pull. The question is not asking from the point in time prior to pulling the trigger the first time.
A couple tried to be too tricky and interpret the question into whether the interviewer should pull the trigger or spin. Obviously spinning does not fire the gun, so choose spinning. Clever, but you missed the important word ‘first’. It said should I spin ‘first’ or just pull the trigger. The addition of the word first maens the trigger will still get pulled.
The science answer, bringing gravity into it does not work because you don’t know what angle the gun is held at when the chamber is spun. If the gun is pointed up, the effect of gravity on the side of the chamber weighed down by two bullets is negated - and pointing the gun up is a safe way to do this.
The real key to this is realizing what information has been learned after the first trigger pull and how that affects the odds. What we know are 3 things. We eliminated one empty chamber from teh first trigger pull. We know the two bullets are adjacent, and we know the barrel will take the next chamber in line on the next trigger pull (not a random chamber). Since we are alive after the first trigger pull, we know one of the two bullets cannot possibly be hit on the next trigger pull since the only way it can be reached is by having first hit the bullet next to it - in which case we’d be dead. That is not the case, therefore, there are only 4 chambers that can be hit on the next pull, and only one bullet in those four can be struck - a 1 in 4 chance.
If you do not spin the barrel, the worst case scenario is that the the next bullet is the first in the group. The chances of getting shot here are 1/4, because you will definitely have to have the first bullet of the group as the next to be fired. That leaves the first bullet spot, plus the three unknown spots to a 1/4 chance. If you spin the barrel, your making the whole thing random. It doesn’t matter if the next bullet is the first or second, either way, your going to get shot and killed if it’s one of those bullets. So the chance of getting shot here is 2/6. And 1/4 chance is less than a 1/3 chance.
I might be the only one who disagrees that the chance of spinning is 2/6. I think if the two bullets are not in ajacent chambers, yes, the chance of spinning is 2/6. If the two bullets are ajacent, the chance is 1/5. In this case, the two ajacent chambes with the bullets could be considers ONE chamber. So, we can think of only one bullet in one chamber out of 5 in the gun.
I agree that the chance of not spinning the barrel is 1/4.
So, comparing the 1/5 and 1/4, you guys know what I am going to choose.
thanks.
Gary
If you were not shot from the first time, and you don’t spin the barrel, there are 4 positions possible. Out of these 4 positions, only 1 will lead to being shot. Therefore, probability is 25%. If you spin the barrel the probability is 33%.
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