Monday, December 12, 2011

Russian Roulette

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 adjacent chambers. I close the barrel and spin it. I put the gun to your head and pull the trigger. Click 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 spun the barrel first or that I just pull the trigger ?

What happens if  the two bullets aren't adjacent to each other in the barrel....

1 comment:

  1. 1st Case:
    Possible combinations of both bullets
    1,2
    2,3
    3,4
    4,5
    5,6
    6,1


    Don't Spin case
    ---------------

    Since you are not shot in the first one so (6,1)& (1,2) doesn't have the bullet's and they are in one of the other possible 4 slots

    P(death)=1/4 = .25
    p(survival)= .75

    Spin it case-
    -------------
    P(death)=2/6=1/3 = .33
    p(survival) = .77

    So don't spin it.

    2nd case:
    Don't Spin It case
    ------------------
    Not hit in the first case so
    P(death) in second hit = 2/5 = .4

    Spin it case
    --------------
    P(death) in second hit = 2/6 = .3

    So he should spin it if bullets aren't adjacent

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