What is the probability of guessing a phone passcode correctly when knowing one digit but not the position of said digit?

Question

The probability of guessing a 4 digit passcode is 1 in 10 000 but what happens when I know one digit but not the position of this digit. This digit could take any of the positions:

_ _ _ X

_ _ X _

_ X _ _

X _ _ _

Would it be correct to calculate it as 4x(1/1000) since there are 10 possibilities for each empty slot and 4 possible positions for the known digit?

Answer 1

You are correct. Nicely done