Permutations And Combinations Question 114
Question: If $ n $ and $ r $ are two positive integers such that $ n\ge r, $ then $ ^{n}{C _{r-1}} $ $ +{{}^{n}}C _{r}= $ [Kerala (Engg.) 2002]
Options:
A) $ ^{n}{C _{n-r}} $
B) $ ^{n}C _{r} $
C) $ ^{n-1}C _{r} $
D) $ ^{n+1}C _{r} $
Correct Answer: D
Show Answer
Answer:
Solution:
$ ^{n}{C _{r-1}}+{{}^{n}}C _{r}={{}^{n+1}}C _{r} $ is a standard formula.
BETA
