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NDA 2011

Exam: NDA
Year: 2011
Subject: Mathematics
Chapter: Permutation and Combination

NDA 2011 · Mathematics · Permutation and Combination

What is the value of ∑_ r=1 ^n P(n, r) r! ?

What is the value of

\sum_{r=1}^n \frac{\mathrm{P}(n, r)}{r!}

?

Options

A $2^n-1$
B $2^n$
C $2^{n-1}$
D $2^n+1$

Correct answer

A. $2^n-1$

Step-by-step solution

The correct answer is option A

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