Maths-
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Question

The total number of 8 digit numbers which have all different digits is

  1. 9 cross times P presuperscript 9 subscript 7
     
  2. blank to the power of 10 end exponent P subscript 8 end subscript    
  3. blank to the power of 10 end exponent P subscript 7 end subscript    
  4. blank to the power of 10 end exponent P subscript 6 end subscript    

Hint:

Total possible ways = Ways of filling 1st place  cross times Ways of filling remaining places 

The correct answer is: 9 cross times P presuperscript 9 subscript 7


    Total digits = 10 ( 0,1,2, ...... 9)
    Ways of filling 1st place = 9 ( zero cannot be placed first)
    Ways of filling remaining places = P presuperscript 9 subscript 7
    Thus, total possible ways = 9 cross times P presuperscript 9 subscript 7

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