# Propability Questions

1. Sep 14, 2013

### PsychonautQQ

1. The problem statement, all variables and given/known data
1.In the game'' of Russian roulette, the player inserts a single cartridge into the drum of a revolver, leaving the other five chambers of the drum empty. The player then spins the drum, aims at his/her head, and pulls the trigger. 1.What is the probability of the player still being alive after playing the game $$N$$ times?
2.What is the probability of the player surviving $$N-1$$ turns in this game, and then being shot the $$Nth$$ time he/she pulls the trigger?
3.What is the mean number of times the player gets to pull the trigger?

3. The attempt at a solution
(I'm in the process of learning LaTex, but for now....)

1. The chances of the person still being with 5 chambers is

$$\sum_{n=zero}^4 \frac{1}{5-n}$$
series from n=0 to n=4 (1/(5-n)
right? This would equate to 1/(5-0) + 1/(5-1) + 1/(5-2) etc etc...

i'm a bit stumped at question #2 however.

Last edited: Sep 14, 2013
2. Sep 14, 2013