Question

If sum of $n$ terms of a series is $S_n=\frac{n(n+1)}{2}$, then $5^{\text{th}}$ term is

Answer 1

$S_n=\frac{n(n+1)}{2}\Rightarrow T_5=S_5-S_4\Rightarrow T_5=\frac{5\times 6}{2}-\frac{4\times 5}{2}\Rightarrow T_5=15-10=5$