# Probability distribution pin code guessing

by Max.Planck
Tags: code, distribution, guessing, probability
 P: 127 1. The problem statement, all variables and given/known data What is the distribution of stochastic variable X = "the number of attempts needed to find the correct last digit of a pin code" 2. Relevant equations 3. The attempt at a solution I thought it was like this: P(X=1) = 1/10 P(X=2) = 9/10*1/9 P(X=3) = 9/10*8/9*1/7 ... ... P(X=10) = 9/10*8/9*7/8*6/7*5/6*4/5*3/4*2/3*1/2*1 Thank you!
HW Helper
P: 4,131
 Quote by Max.Planck 1. The problem statement, all variables and given/known data What is the distribution of stochastic variable X = "the number of attempts needed to find the correct last digit of a pin code" 2. Relevant equations 3. The attempt at a solution I thought it was like this: P(X=1) = 1/10 P(X=2) = 9/10*1/9 P(X=3) = 9/10*8/9*1/7 ... ... P(X=10) = 9/10*8/9*7/8*6/7*5/6*4/5*3/4*2/3*1/2*1 Thank you!
Looks good.

RGV
P: 127
 Quote by Ray Vickson Looks good. RGV
Thanks. Is it possible to capture P(X=x) in a formula?