If P (n, n) denotes the number of permutations of n different things taken all at a time…
Mathematics · JEE Advanced · NTA Exams — Permutations and Combinations
If P (n, n) denotes the number of permutations of n different things taken all at a time then P (n, n) is also identical to
- r ! P (n, n – r)
- (n – r) . P (n, r)
- n . P (n – 1, n – 1)
- P (n, n – 1)
where 0 < r < n
Answer
(A) r ! P (n, n – r), (C) n . P (n – 1, n – 1), (D) P (n, n – 1) where 0 < r < n
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