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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kavitaKumari · Answer 1 · 2021-06-28T05:49:58+0000

Digits 6, 7 already used, so only 8 digits available to fill remaining 3 places.

6

7

6 ways

7 ways

8 ways

Hence by fundamental principle of counting there are 8 × 7 × 6 = 336 different 5 digit telephone numbers.