A) 10
B) 15
C) 9
D) 5
Correct Answer: C
Solution :
\[{{\,}^{n}}{{P}_{4}}=24\,{{\,}^{n}}{{C}_{5}}\Rightarrow \frac{n!}{n-4!}=\frac{24\,n!}{5!n-5!}\] \[\Rightarrow \]\[\frac{n!}{(n-4)n-5!}=\frac{24n!}{5!n-5!}\] \[\Rightarrow \]\[\frac{1}{n-4}=\frac{24}{5.4.3.2}\Rightarrow \frac{1}{n-4}=\frac{1}{5}\] \[\Rightarrow \]\[n-4=5\Rightarrow n=9\]You need to login to perform this action.
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