There is a 7-digit telephone number with all different digits . If the digit at extreme right and extreme left are 5 and 6 respectively, find how many such telephone numbers are Possible.

• 6 8*7*6*5*4* 5=6720
• 8 years agoHelpfull: Yes(0) No(0)
• There are 5 more digits are to be selected and arranged from 8 digits (0,1,2,3,4,7,8,9).
  As this involves selection and arrangement, it is a nPr problem but not nCr.
  8P5 = 8!/3! = 8*7*6*5*4 = 6720
• 7 years agoHelpfull: Yes(0) No(0)