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The number of five digit telephone numbers having at least one of their digits repeated is `90000` b. `100000` c. `30240` d. 69760

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The number of five digit telephone numbers having at least one of their digits repeated is `90000` b. `100000` c. `30240` d. 69760
A. 90000
B. 27216
C. 62784
D. 15120
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We have,
Total number of five digit numbers `=9xx10xx10xx10xx10=90000`
and
Total number of five digit numbers with distinct digits
`=(""^(10)C_(5)xx5!-""^(9)C_(4)xx4!)=27216`
`:.` Number of numbers having at least one repeated
`=90000-27216=62784`
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