A) 4
B) 8
C) 6
D) 7
Correct Answer: B
Solution :
\[\frac{n\ !}{(n-5)\ !}\times \frac{(n-3)\ !}{n\ !}\]=20 \[\Rightarrow \]\[(n-3)(n-4)=20\Rightarrow n=-1,\ 8\] But \[-1\] is not exceptable.You need to login to perform this action.
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