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How many five digits telephone numbers can be constructed using the digits 0 to 9 if each number starts with 67 and no digit appears more than once? |
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Answer» Digits 6, 7 already used, so only 8 digits available to fill remaining 3 places.
Hence by fundamental principle of counting there are 8 × 7 × 6 = 336 different 5 digit telephone numbers. |
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