Question

Jack has a pin number that he uses to access his bank account. his code consists of 4 different numbers from 0 to 9. what is the probability that someone could guess his code?

Answer 1

Actually the correct probablity should be:
$\frac{1}{5040}$
The answer given by the previous user is incorrect.

Answer 2

For each choice of the first two digits you have 10 choices for the third digit. Thus you have 10x10x10 = 1000 choices for the first three digits. Finally you have 10choices for the fourth digit and thus there are 10x10x10x10 = 10 000 possible 4 digit combinations from 0-9.