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).

Asked by rajeev bhatia | 16th Feb, 2012, 03:01: PM

Expert Answer:

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.

Answered by  | 17th Feb, 2012, 10:03: AM

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