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 $ .