Question

Which term of the series $5,8,11,14,$ .. is $320$ ?

• A. ${104}^{th}$
• B. ${105}^{th}$
• C. ${106}^{th}$
• D. ${64}^{th}$

Answer 1

The correct option is C ${106}^{th}$

Clearly, $5+3=8,8+3=11,11+3=14,$
So, the series is an A.P. in which $a=5$ and $d=3.$
Let $320$ be the $n^{th}$ term of the series.
Then, $320=5+(n-1)\times 3$ or $(n-1)$ = $105$ or $n$ = $106.$