(i) If `""^(n)P_(4): ""^(n)P_(5)=1:2`, find n. (ii) If `""^(n-1)P_(3): – InterviewSolution

InterviewSolution

1.	(i) If `""^(n)P_(4): ""^(n)P_(5)=1:2`, find n. (ii) If `""^(n-1)P_(3): ""^(n+1)P_(3)=5:12`, find n.
Answer» Correct Answer - (i) n = 6 (ii) n = 8 (ii) `((n-1)(n-2)(n-3))/((n+1)n(n-1))=(5)/(12) rArr 12(n-2)(n-3)=5(n+1)n ` `rArr 7n^(2)-65n+72=0 rArr 7n^(2)-56n-9n+72=0` `rArr 7n(n-8)-9(n-8)=0 rArr (n-8)(7n-9)=0 rArr n=8.`

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