Let the number be _ _ _ First place can be filled in 9 ways : 1 to 9 2nd place again in 9 ways : omitting the digit used in irst place but now we can use 0 also. 3rd place: 8 ways as we now we have one digit lesser than earlier if we want to prevent repitition. so answer is 9 x 9 x 8 = 648 such numbers. :)
Moderation Team
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