A) 1
B) 2
C) 4
D) 5
Correct Answer: B
Solution :
\[\left( \frac{(2n)\ !}{2\ !\ (2n-2)\ !} \right)\,\,2=\left( \frac{n\ !}{2\ !(n-2)\ !} \right)\,\,9\] \[\Rightarrow (2n)(2n-1)2=9n(n-1)\Rightarrow n=5\] Now\[^{5}{{C}_{r}}=10\Rightarrow r=2\].You need to login to perform this action.
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