An ATM pin number is 4 digits long using digits 0 through 9

An ATM pin number is 4 digits long using digits 0 through 9 with repeats allowed. What is the probability of randomly guessing a particular pin number?

Solution

Total number of possible pins = 10*10*10*10 = 10000

Probability of guessing correct one is 1 in 10000 or 1/10000 = 0.0001