permutation

Two n digit integers are said to be equivalent if one is a permutation

of the other. for eg. 10075 and 01057 are equivalent.

Find the number of 5 digit integers such that no two are equivalent

3 Answers

This question is same as number of 5 digit numbers a₁a₂a₃a₄a₅ such that

a₁>=a₂>=a₃>=a₄>=a₅

Now it should be easy?

I can not understand your hint :-(

see teh hint says that if you arrange a1>a2>a3>a4>a5, then any other arrangement of these numbers will be equivalent.

So just by counting all such arrangements, we are done

for instance lets take the case when there are 3 digits only..

then 4,2,1 will represent all arrangements : 1,2,4; 1,4,2; 2,4,1; 2,1,4; 4,1,2; 4,2,1

That is what i meant!

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