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permutation and Combination fall 2011

permutation and Combination fall 2011 - DSCI 2710 SC...

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1 DSCI 2710 Permutation and Combination How Many 4-digit PIN Numbers are Possible? We need to know what are the possible values for each digit. We need to know if a number can be repeated.
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2 Assume Repetition Is Allowed Assume that each PIN digit can be chosen from 0 to 9. If repetition is allowed , then the number of codes is 10 * 10 * 10 * 10 = 10 4 = 10,000 Assume No Repetition Is Allowed Si di it t b Since a digit cannot be repeated, the number of choices decreases each time. The number of possible codes is 10 * 9 * 8 * 7 = 5040.
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