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If there are 10,600 people born in the United States each day, what is the probability that one of them would have the same last four digits of my social security number?

Consider the number of ways that the last four digits of a social security number can be formed: 10^4=10,000. Each gets 9999 out of 10000 chances to have other than your social security number. If the last four digits are effectively random, then the probability that everybody gets other than your digits is (9999/10000)^10600. This subtracted from one is the probability that at least one person gets your digits.

Kenneth Mellendorf

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