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A nine-digit number is formed using the digits 1,   2 ,   3,   5 and 7 . The probability that the product of all digits is always 1920 is

Options

  1. A1 5 9
  2. B7 5 8
  3. C72 5 9
  4. D1 7 !

Correct answer

C. 72 5 9

Step-by-step solution

Total cases = 5 9 1920 = 5 × 3 × 2 7 Favourable cases = no. of ways of arrangement of 5,3 , 2,2 , 2,2 , 2,2 , 2 in a row = 9 ! 7 ! hence, required probability = 72 5 9

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