Permutations And Combinations Question 115
Question: If $ ^{43}{C _{r-6}}={{}^{43}}{C _{3r+1}}, $ then the value of r is [Kerala (Engg.) 2002]
Options:
A) 12
B) 8
C) 6
D) 10
 Correct Answer: AShow Answer
  Answer:
Solution:
Þ  $ r-6=3r+1 $  or  $ r-6+3r+1=43 $
Þ  $ r=-\frac{7}{2} $  (impossible) or  $ r=12 $ .
 BETA
  BETA 
             
             
           
           
           
          