Answer: 1/5040
Step-by-step explanation:
There are 10 possible digits for the first digit, 9 possible digits for the second, 8 for the third, and 7 for the fourth, as digits can't repeat. Thus, there are 10 x 9 x 8 x 7 = 5040 combinations. The probability of getting it on the first try is 1/5040.