SATHEE: Permutations And Combinations Question 84

Permutations And Combinations Question 84

Question: If $ ^{15}C _{3r}{{=}^{15}}{C _{r+3}} $ , then the value of $ r $ is [IIT 1967; RPET 1991; MP PET 1998; Karnataka CET 1996]

Options:

A) 3

B) 4

C) 5

D) 8

Show Answer

Answer:

Correct Answer: A

Solution:

$ ^{15}C _{3r}{{=}^{15}}{C _{r+3}}{{\Rightarrow }^{15}}{C _{15-3r}}{{=}^{15}}{C _{r+3}} $

$ \Rightarrow 15-3r=r+3\Rightarrow r=3 $ .

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Permutations And Combinations Question 84

Question: If $ ^{15}C _{3r}{{=}^{15}}{C _{r+3}} $ , then the value of $ r $ is [IIT 1967; RPET 1991; MP PET 1998; Karnataka CET 1996]

Options:

Answer:

Solution:

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