Jessica cannot remember the correct order of the five digits in her id number. she does remember that the id number contains the digits 9, 0, 3, 1, 5. what is the probability that the first four digits of jessica’s id number will all be odd numbers?

Well 4 out of the 5 are odd.  So the probability the first digit is odd is (4/5) since that digit is no longer available, then the probability the second digit is odd is (3/4), then for the third (2/3), then the forth (1/2).

So to find the first four being odd is (4/5)*(3/4)*(2/3)*(1/2) = 24/120 = .20