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If an=sum(r=0)^n1/(""^nCr) , then sum(r=...

If `a_n=sum_(r=0)^n1/(""^nC_r)` , then `sum_(r=0)^nr/(""^nC_r)` equals :

A

`(n-1)a_n`

B

`na_n`

C

`1/2na_n`

D

None of these

Text Solution

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The correct Answer is:
C
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