SOLUTION: A serial number on a 5$ bill includes 3 letters followed 7 digits. Assuming the digits are randomly assigned, what is the probability that the serial number will contain at least f
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-> SOLUTION: A serial number on a 5$ bill includes 3 letters followed 7 digits. Assuming the digits are randomly assigned, what is the probability that the serial number will contain at least f
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Question 1153090: A serial number on a 5$ bill includes 3 letters followed 7 digits. Assuming the digits are randomly assigned, what is the probability that the serial number will contain at least five even digits? What is the average number of even digits that will appear in a serial number? Answer by greenestamps(13200) (Show Source):
The probability that any one digit is even is 1/2; the probability that it is odd is 1/2.
(1) P(5 of the 7 are even (and 2 are odd)) =
(2) P(6 of the 7 are even (and 1 is odd)) =
(3) P(7 of the 7 are even (and 0 are odd)) =
ANSWER: P(at least 5 are even) = 29/128
Without doing any fancy calculations, since the probabilities of each digit being even or odd are the same, on average half of the 7 digits will be even.
