Thu February 16, 2012 By: Rajeev Bhatia

with 2,3,4,5 how many numbers forms taking 4 digits . (ans:4p4=24)my ques. is how many times each digit occurs in unit and all places ie. hundreds,tens,thousand . (ans:phactorial 3 =6 can we explain this answer ie. 6 with permutaion formula nPr).

Expert Reply
Fri February 17, 2012
lets fix the units digit as 2,
then the number of ways in which the remaining three digits can be placed in three places is factorial 3
the same can be understood as the number of ways of selecting three digits for three places
which will be 3p3=factorial 3.
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