A social security number has 9 digits so there are 1x10^9 possible different numbers. If the US population is about 300 million, how many social security numbers are available for each person?
300 million = 3 x 108
So we have
[1 x 109 ] / [ 3 x 108 ] =
(1/3) X 10 = about 3 numbers per person
