Permutations And Combinations Question 185
Question: If $ ^{n}C _{r}={{}^{n}}{C _{r-1}} $ and $ ^{n}P _{r}{{=}^{n}}{P _{r+1}} $ , then the value of n is
Options:
A) 3
B) 4
C) 2
D) 5
Correct Answer: A The condition provided that $ n - r = r - 1 $
Þ $ r=\frac{n+1}{2} $ . So if we put $ n=3 $ , then $ r=2 $ satisfies the conditions.
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Answer:
Solution:
BETA
