SATHEE: Permutations And Combinations Question 188

Permutations And Combinations Question 188

Question: If $ ^{n}P _{r}=840,{{}^{n}}C _{r}=35, $ then $ n $ is equal to [EAMCET 1986]

Options:

A) 1

B) 3

C) 5

D) 7

Show Answer

Answer:

Correct Answer: D

Solution:

$ \frac{^{n}P _{r}}{^{n}C _{r}}=24\Rightarrow r\ !=24\Rightarrow r=4 $

$ \therefore $ $ ^{n}C_4=35\Rightarrow n=7 $ .

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Permutations And Combinations Question 188

Question: If $ ^{n}P _{r}=840,{{}^{n}}C _{r}=35, $ then $ n $ is equal to [EAMCET 1986]

Options:

Answer:

Solution:

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