Question

If the $n\text{th}$ term of a sequence is given by $t_n=8n+3$, then the sum of first $20$ terms is

• A. $1720$
• B. $1330$
• C. $1800$
• D. $1740$

Answer 1

The correct option is D $1740$

Given : $t_n=8n+3$
As it is a linear function in $n$, so it is an A.P. with
$t_1=11t_{20}=163$
Therefore, the sum of $20$ terms
$S_{20}=\frac{20}{2}[11+163]\therefore S_{20}=1740$