SOLUTION: What is the probablity that a seven-digit telephone number has one or more repeated digits? Assume no one digit is more likely than another to be used. In addition, the leading dig

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Question 566666: What is the probablity that a seven-digit telephone number has one or more repeated digits? Assume no one digit is more likely than another to be used. In addition, the leading digit cannot be zero.
Answer by stanbon(75887) About Me  (Show Source):
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What is the probablity that a seven-digit telephone number has one or more repeated digits? Assume no one digit is more likely than another to be used. In addition, the leading digit cannot be zero.
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Pattern: ------- where lead digit is not zero
Total number: 9*10^6 = 9 million with repeates
Total number with no repeats: 9*9*8*7*6*5*4 = 544320
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P(1 or more repeated digits) = 1 - (544320]/9000000) = 0.9395
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Cheers,
Stan H.