Question

If the $n^{th}$ term of a sequence is given by $t_n=7n-9$, then the sum of first $100$ terms is

• A. $34455$
• B. $34450$
• C. $35450$
• D. $35550$

Answer 1

The correct option is B $34450$

As $t_n=7n-9$, which is a linear function of $n$, so it is an A.P.
$a=t_1=-2d=t_2-t_1=7$

Now, the sum of first $100$ terms
$S_{100}=\frac{100}{2}[2\times (-2)+99\times 7]\therefore S_{100}=34450$