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Iff ""^(5)P(r)=""^(6)P(r-1) find r....

Iff `""^(5)P_(r)=""^(6)P_(r-1)` find r.

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The correct Answer is:
i. r = 3, since `""^(5)P_(10)` is not defined
ii. `r` = 3, since `""^(4)P_(8)` is not defined
iii. `r` = 4, since `""^(5)P_(9)` is not defined
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NEW JOYTHI PUBLICATION-PERMUTATIONS AND COMBINATIONS-QUESTIONS FROM COMPETITIVE EXAMS
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  15. If ""^(n)C(3)=220, then n = ?

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