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 If Pr stands for   Pr  n then sum of the series 1+P1+ 2P2+3P3++nPn is 

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a
(n+1)!
b
Pn+1−1
c
Pn-1+1
d
none of these

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detailed solution

Correct option is A

1+P1+2P2+3P3+…+nPn=1+1!+2(2!)+3(3!)+…+n(n!)=1+∑r=1n [(r+1)−1]r!=1+∑r=1n {(r+1)!−r!}=1+(n+1)!−1!=(n+1)!


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