SATHEE: Permutations And Combinations Question 244

Permutations And Combinations Question 244

Question: If $ {}^{n}P_4\ :\ {}^{n}P_5=1:2 $ , then $ n= $ [MP PET 1987; RPET 1996]

Options:

A) 4

B) 5

C) 6

D) 7

Show Answer

Answer:

Correct Answer: C

Solution:

$ \frac{n\ !}{(n-4)\ !}\times \frac{(n-5)\ !}{n\ !}=\frac{1}{2}\Rightarrow n-4=2\Rightarrow n=6 $ .

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Permutations And Combinations Question 244

Question: If $ {}^{n}P_4\ :\ {}^{n}P_5=1:2 $ , then $ n= $ [MP PET 1987; RPET 1996]

Options:

Answer:

Solution:

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