A small combination lock on a suitcase has 3 wheels, each labeled with the 10 digits from 0 to 9.

Question

A small combination lock on a suitcase has 3 wheels, each labeled with the 10 digits from 0 to 9. If an opening combination is a particular sequence of 3 digits with no repeats, what is the probability of a person guessing the right combination?

Answer 1

You have to determine how many 3-digit permutations you can form using the digits from 0 to 9 with no repeats.

for the first digit you are choosing from 10 digits

for the second digit you are choosing from 9 digits

for the third digit you are choosing from 8 digits

10*9*8=720

the probability that the person guesses the correct 3-digit sequence is 1/720