Question

Every US. Citizen has a 9 digit social security number. The first 3 digits are a geographic code, the next two digits are determined by the year, and the state where the number is issued, and the last four digits are random numbers. If you are less than 100 years old, what is the probability that the last two numbers are your age?

Answer 1

Probability of success =

         (number of possibilities that would be considered successful)
divided by
         (total number of different possible outcomes) .

Total number of different possible outcomes =

       total number of different possible values of the last 2 digits

   =  the quantity of numbers from  00  to  99

   =    100 of them .

The number of possibilities that will match your age  =  only 1 .

Probability that the last 2 digits match your age = 1/100  =  0.01  =  1 % .