vaibhav katore answered question 2/11/2011 How Many 4-digit Numbers Can Be Formed Using The Digits 0,1,2,3,4,5,6 If Repetition Of Digits Is Not Allowed? There are (7!)/(7-4)! = 7*6*5*4 permutations of 7 numbers taken 4 at a time. That's 840.
