A) 35
B) 46
C) 23
D) \[4k+1\](where\[K\in {{l}^{+}}\]
Correct Answer: C
Solution :
\[^{n}{{C}_{r}}{{:}^{n}}{{C}_{4+1}}{{:}^{n}}{{C}_{r+2}}=1:7:35\] \[\Rightarrow \]\[\frac{r+1}{n-r}=\frac{1}{7}\Rightarrow 8r=n-7\] \[\And \frac{r+2}{n-(r+1)}=\frac{1}{5}\Rightarrow 6r=n-11\] Solving above equations n = 23You need to login to perform this action.
You will be redirected in
3 sec