on may 5, 2013, savant made an error in a combinatorics problem. the question was how many different 4-digit briefcase combinations contain a particular digit (say 5, for example). she said the answer was 4000, yet people showed the correct answer—3439—using various strategies. the incorrect answer of 4000 counted those combinations with more than one "5" multiple times (twice for "1535", three times for "1555", for instance). so, the correct answer is to take all possible combinations minus the combinations in which each digit is not a 5 to the n power, or 10,000 - 9 = 3439.