SATHEE: Permutations And Combinations Question 194

Permutations And Combinations Question 194

Question: If $ ^{n}P_4=30{{}^{n}}C_5 $ , then $ n= $ [MP PET 1995]

Options:

A) 6

B) 7

C) 8

D) 9

Show Answer

Answer:

Correct Answer: C

Solution:

$ \frac{^{n}P_4}{^{n}C_5}=30\Rightarrow \frac{n\ !}{(n-4)\ !}\times \frac{5\ !\ .\ (n-5)\ !}{n\ !}=30 $

$ \Rightarrow (n-4)=4\Rightarrow n=8 $ .

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Permutations And Combinations Question 194

Question: If $ ^{n}P_4=30{{}^{n}}C_5 $ , then $ n= $ [MP PET 1995]

Options:

Answer:

Solution:

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