A) 5
B) 10
C) 12
D) 14
E) 20
Correct Answer: D
Solution :
Given that, \[a=3,\text{ }d=4,\text{ }5=406\] \[\therefore \] \[406=\frac{n}{2}[6+(n-1)4]\] \[\Rightarrow \] \[406=n(2n+1)\] \[\Rightarrow \] \[2{{n}^{2}}+n-406=0\] \[\Rightarrow \] \[(n-14)(2n+29)=0\] \[\Rightarrow \] \[n=14\] \[\left( \because n\ne -\frac{29}{2} \right)\]You need to login to perform this action.
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