a forgets telephone no of b. he remembers is no had 8 digits and ended with odd no and had exact one 9.how many possible nos a try to have to be sure he gets correct no??

• case 1) 9 is at the end which is odd.
  and we have to chose exactly one 9.
  so the place of 9 is at the end.
  remaining all the 7 digit will contain numbers from 1,2,3,...8
  i.e. 8C1*8C1*8C1*8C1*8C1*8C1*8C1*1=8*8*8*8*8*8*8*1
  or......
  case 2)the number ended with odd number and it is not 9 that means last digit of the number will contain any one of 1,3,5,7 and remaining 7 digit will contain any number from 1,2,3,...8 and 9 will be fitted any one of 7 places.
  i.e.7(9C1*8C1*8C1*8C1*8C1*8C1*8C1*4C1)=7*9*8*8*8*8*8*8*4
  therefore no of chances will be.
  8*8*8*8*8*8*8*1+7*9*8*8*8*8*8*8*4
• 11 years agoHelpfull: Yes(1) No(0)
• 1*9*9*9*9*9*9*4
  1 for 9 no. which is fixed
  9 for any digit can be selected
  4 for odd no. excluding 9
  
• 11 years agoHelpfull: Yes(0) No(0)
• ans is 300.9^5
• 11 years agoHelpfull: Yes(0) No(0)
• but how xplain pls??
• 11 years agoHelpfull: Yes(0) No(0)