Asocial security number consists of nine digits in a particular order, and repetition of digits is allowed. after seeing the last four digits printed on a receipt, if you randomly select the other digits, what is the probability of getting the correct social security number of the person who was given the receipt? what is the formula?

You have to guess the first 5 digits.

You can calcualte the number of possible numbers that exist with 5 digits.

The first digit cannot be 0, it can be any from 1 to 9, so those are 9 diferent digits.

For the second, third, fourth and fifth digits there are 10 diferent posibilities for each: 0 through 9.

Then, there are 9*10*10*10*10 = 90,000 different possible social security numbers once the last four digits are known.

And the probability to get the correct social security number of the person is 1 /90,000 = 0,000011.