there is a 7 digit telephone no with all different digits. if the digit at extreme right and extreme left are 5 and 6 respectively,find how many such telephone nos are possible

• there is a 7 digit telephone no with all different digits. if the digit at extreme right and extreme left are 5 and 6 respectively
  then possible numbers are 8*7*6*5*4 = 6720.
• 12 years agoHelpfull: Yes(16) No(3)
• The digits at the extreme right and left are 5 and 6 resp.
  So, the 7 digit number is : 6 _ _ _ _ _ 5
  Since repetition of digits are not allowed the second digit can be chosen from (0,1,2,3,4,7,8,9) 8 of the remaining digits. Similarly, the third is chosen from 7, 4 digits is selected from 6 and so on...
  
  So, ANSWER: 8*7*6*5*4 = 6720
• 12 years agoHelpfull: Yes(10) No(3)
• From the question,
  6 _ _ _ _ _ 5
  Deals about arrangement(Permutation), we cant repeat the digits..
  6 and 5 are already present, remaining digits are 01234789= 8digits
  5 spaces are left, hence 8P5=6720
• 12 years agoHelpfull: Yes(7) No(1)
• @dipin : u r wrong ,the nums can be repeated so u cant jusz use 8*7*6*5*4
• 12 years agoHelpfull: Yes(2) No(4)
• sry m wrng dint read the questn properly
• 12 years agoHelpfull: Yes(2) No(0)
• ans-2520
  since leaving extreme right and extreme left no which are fixed(ie,5 and 6)
  the rest 5 numbers can be combined in 7p5 ways. therefore answer =2520 on calculating
• 12 years agoHelpfull: Yes(0) No(6)
• answer is 3360
  we have to select 5 digit from 8 digits(0,1,2,3,4,7,8,9)
  we can select the above as 8c5=56 ways
  the five digits can be interchanged among themselves by 5!=60 ways
  so answer is 8c5*5!=56*60=3360
• 12 years agoHelpfull: Yes(0) No(3)