What is the probability of someone correctly guessing your Social Security number? (Assume all digits 0-9 are available for use)a

Answer: 1 / 999,999,999Explanation:You can do it in two different ways. 1) First approachprobability = number of positive events / number of possible eventsi) number of positive events = 1 (your number is just one number)ii) number of possible events = number of valid numbersAssuming the smallest valid number is 1, and the greatest one is 999,999,999, that leads to 999,999,999 different numbers iii) probability = 1 / 999,999,9992) Second approachi) there are 9 digits.ii) the guesser must guess all the digits in the correct orderiii) since there are 10 digits, from 0 to 9, there are 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 = 1,000,000,000 different combinationsBut that includes the number 000,000,000 which is not valid, so you have to subtract 1: 1,000,000,000 - 1 = 999,999,999Which leads to the same result of the first approach.

[tex]\frac{1}{10^9}=\frac{1}{1000000000}
[/tex]