Russian Roulette
Goldman Sachs
There are two adjacent bullets in a 6 chamber revolver. You put the gun to your head and pull the trigger, and the chamber is empty. If you had to shoot another round, would you pull the trigger again or spin the barrel?
Answer
If we re-spin, our chances of getting killed will be the same as they were for the first spin - 2/6 - since 2 of the 6 chambers contain a bullet. If we don't chose to re-spin, our chances depend on the empty chamber that was just fired. Only one of the 4 empty chambers is followed by a bullet-filled chamber (in the direection of barrel spins). And if this is the one we've just fired, the next barrel contains a bullet and we'll be killed on the next shot. The chance of this is 1/4, since the remaining 3 empty chambers are harmless. Note $\frac{1}{4}\lt \frac{2}{6}$, so our chance of getting shot is higher if we re-spin. We should therefore not re-spin and just fire straight away.