Question

What is the probability that you will get a 3-digit combination correct if no digits in the combination can be repeated?

A. 1/10
B. 1/504
C. 1/720

Answer 1

We can break this problem down digit by digit.
For the first digit, there are 10 possibilities 0 through 9, since no digits have been used.
For the second digit, there are 9 possibilities, since one digit has already been used.
For the third digit, there are 8 possibilities, since 2 have been used.
So, the 3-digit combination has 10*9*8 possible combinations, or 720 possible combinations. That means any one random combination has a 1/720 chance of being the correct one.